The Chemistry and Biological Activities of Peptides from Amphibian

Review pubs.acs.org/CR

The Chemistry and Biological Activities of Peptides from Amphibian Skin Secretions Xueqing Xu†,‡ and Ren Lai*,† †

Key Laboratory of Animal Models and Human Disease Mechanisms of Chinese Academy of Sciences & Yunnan Province, Kunming Institute of Zoology, Kunming 650223, Yunnan, China ‡ School of Pharmaceutical Sciences, Southern Medical University, Guangzhou 510515, China 2.8. Lectins 2.9. Insulin-Releasing Peptides 2.10. Mast Cells Degradation/Histamine-Releasing Peptides 2.11. Wound-Healing Peptides 2.12. Immunomodulatory Peptides 2.13. Neuronal Nitric Oxide Synthase Inhibitors 2.14. Antimicrobial Peptides from Amphibian Skin Secretions 2.14.1. Alytes 2.14.2. Ascaphus 2.14.3. Bombina 2.14.4. Hoplobatrachus 2.14.5. Kassina 2.14.6. Leptodactylus 2.14.7. Litoria 2.14.8. Hylarana 2.14.9. Hyla 2.14.10. Pseudis 2.14.11. Hypsiboas 2.14.12. Agalychnis, Hylomantis, and Pachymedusa 2.14.13. Phyllomedusa 2.14.14. Uperoleia 2.14.15. Crinia 2.14.16. Xenopus 2.14.17. Silurana 2.14.18. Hymenochirus 2.14.19. Amolops 2.14.20. Pelophylax 2.14.21. Limnonectes 2.14.22. Bufo 2.14.23. Ceratophrys 2.14.24. Lithobates 2.14.25. Odorrana 2.14.26. Rana 2.15. Antiviral Peptides 2.16. Antitumor Peptides 2.17. Antiparasite Peptides 2.18. Pheromone Peptides 2.19. Granins 2.20. Others 3. Summary Author Information Corresponding Author

CONTENTS 1. Introduction 2. Structures and Functions of Amphibian Peptides 2.1. Myotropical Peptides 2.1.1. Bradykinins 2.1.2. Bombesins 2.1.3. Tachykinins 2.1.4. Tryptophyllins 2.1.5. Caeruleins 2.1.6. Cholecystokinins 2.1.7. Other Myotropical Peptides 2.2. Opioid Peptides 2.2.1. Dermorphins 2.2.2. Deltorphins 2.2.3. Other Peptides with Analgesic Functions 2.3. Corticotropin-Releasing Peptides 2.4. Angiotensins 2.5. Protease Inhibitor Peptides 2.5.1. ORB Family 2.5.2. Kunitz/Bovine Pancreatic Trypsin Inhibitor (BPTI) Family 2.5.3. The Biological Roles of Proteinase Inhibitory Peptides in Amphibian Skins 2.6. Neuropeptides 2.6.1. FMRFamide Peptides 2.6.2. Bv8 2.6.3. Neuromedin U 2.6.4. Neuropeptide Y Family 2.6.5. Xenoxins 2.6.6. Neurotoxins 2.6.7. Levitide 2.6.8. Rothein 1 2.6.9. Small Neuropeptides Containing One Disulfide Bridge 2.7. Antioxidant Peptides © XXXX American Chemical Society

B B B B I I J J J K K L L L L M M M N N N N P P P P P P Q Q S

S S U V W W Y Y Y AC AC AD AD AD AG AM AM AM AM AM AO AO AO AO AS AU AU AU AU AY AY AY BK BN BN BT BU BU BV BV BV BV

Received: November 25, 2013

A

DOI: 10.1021/cr4006704 Chem. Rev. XXXX, XXX, XXX−XXX

Chemical Reviews Notes Biographies Acknowledgments Abbreviations References

Review

BK-like peptides have been reported in amphibian skin secretions (Table 1). However, a BRP present in one species does not always appear in the skin secretions of closely related species. Amphibian skin kininogens have been reported by different studies focusing on toads in the genus Bombina. The scope of BK variants and the structural organization of their skin precursors are very different even among congeneric amphibian species. BK variants are derived from the nonapeptide (RPPGFSPFR) itself or are products of extensions at its C-terminus or N-terminus. For example, the precursor encoding bombinakinin M from Bombina maxima skins contains 6 tandem-repeat domains, each encoding a peptide.28 Two different precursors encode BK and (Thr6) bradykinin in Bombina orientalis skin, which contain 4 and 2 tandem repeats of peptide-encoding sequence, respectively.26 Two precursors encode, respectively, a single copy of (Ala3, Thr6) bradykinin and (Val1, Thr3, Thr6) bradykinin from Bombina variegata skin.27 Amphibians survive in various conditions with many predators and pathogens, and BK-like peptides in amphibian skin might have defensive functions alone or synergistically with other components. The diversity of BRPs in amphibian skin secretions reflects and might be dictated by their range of species-specific predators.29 Although increasing numbers of BK-like peptides are reported from amphibian skin,16−28 their structure−function relationships have not been well researched. In general, BK-like peptides have various extensions on the N-terminus and/or Cterminus of a conserved PPGF motif. For example, both bombinakinin M and its variant in the skin secretions of the toad B. maxima contain 19 amino acids (aa) that extend BK from its N-terminus with DLPKINRKGP and DLSKMSFLHGI.28 Despite containing a BK moiety on the C-terminus, bombinakinin M is a BK receptor agonist with dose-dependent contractile activity in the guinea pig ileum, while the bombinakinin M variant does not have this activity. Thus, their functional difference is derived from the different N-termini segments of two peptides. This suggests that the effect of the N-terminal and C-terminal extensions of BRPs from amphibian on BK function is more elusive than previously thought. Some peptides from amphibian skin can potentiate or inhibit BK function. Phypo Xa, a BK potentiating peptide from Phyllomedusa hypochondrialis, might be a natural inhibitor of angiotensin-converting enzymes. Phypo Xa is a canonical peptide with typical pyroglutamyl (Pyr)/proline-rich classical motif sequences at the C-terminus that potentiate BK activity in vivo and in vitro and efficiently competitively inhibit angiotensin-converting enzymes.30 Des (Arg9, Leu8) bradykinin is a potent BK B1 receptor antagonist.31 Odorranaopin (DYTIRTRLHQESSRKVL) inhibits the contractile effect induced by BK, possibly by blockade of BK or BK receptor functions.32 Analgesin a1 and analgesin a2 from the skin secretions of the tree frog Hyla simplex have an antinociception effect through signal pathways associated with BK.33 BRPs can be produced from circulating kininogens of typical species of different vertebrate taxa by trypsin treatment.34 However, amphibian plasma treated with enzymes generates an angiotensin-like peptide, not a BRP.29 Many studies have reported cDNA sequences encoding precursors of frog skin BRPs.8,21−24,26,27,35−37 These findings indicate that skin preproBK structures are not related to plasma kininogens; thus frog skin BRPs are not the products of enzyme catalysis by the kallikrein−kinin system. However, extensive studies on the

BV BW BW BW BW

1. INTRODUCTION Amphibian skin is directly exposed to different environments. Amphibians interact with environmental factors including microorganisms, parasites, predators, and physical factors. The special niche of amphibians is as animals that bridge the evolutionary water−land gap. Therefore, they provide valuable information about prospective functional molecules. Amphibian skin has extreme chemical diversity and is a versatile organ important for everyday survival. Amphibian skin secretions are a subject of interest because of the skin’s unique chemical properties and biosynthesis pathways and because of its potential clinical applications. Over the past several decades, bioactive components of amphibian skin secretions, especially biologically active peptides, have been extensively studied.1−5 More than 100 families of peptides including about 2000 from amphibian skin are discussed in this Review. The peptide families are myotropical peptides, opioid peptides, corticotropin-releasing peptides, angiotensins, protease inhibitor peptides, neuropeptides, antioxidant peptides, lectins, insulinreleasing peptides, mast cells degradation/histamine-releasing peptides, wound-healing peptides, immunomodulatory peptides, neuronal nitric oxide synthase inhibitors, antimicrobial peptides, antiviral peptides, antitumor peptides, antiparasite peptides, pheromone peptides, granains, and other peptides. These peptides are stored in skin granular glands and can be released in high concentrations into skin secretions when the amphibian is stressed or injured. Skin extracts of frogs and toads have been used as traditional medicine for centuries, for example, as Chinese traditional medicine to regulate internal bodily functions and fertility and as ancient Egyptian drugs to treat pain and diarrhea.1,2,6,7 Exploration of the structures and biological functions of active peptides from amphibian skin secretions is important for developing new therapeutic agents. 2. STRUCTURES AND FUNCTIONS OF AMPHIBIAN PEPTIDES 2.1. Myotropical Peptides

The myotropical peptides in amphibian skins include bradykinin (BK), bombesin, tachykinin (TK), tryptophyllin (TPH), caerulein, and cholecystokinin (CCK), which are vital for amphibian defensive mechanisms. These and related peptides exert contractile effects on isolated ileum and smooth muscles. 2.1.1. Bradykinins. Amphibian BK peptides are counterparts to mammalian BKs, which have a wide range of bioactivities in pathophysiological conditions including smooth muscle contraction, hypotension, vasodilatation, pain, and inflammation. The first BK nonapeptide was reported from Rana temporaria frog skin extracts in 1965,8−11 and analogs such as (Val1, Thr6) bradykinin and C-terminally extended molecular forms such as ranakinin N, kinin O, and phyllokinin have been identified.12−15 Many BKs and BK-related peptides (BRPs) have been reported in skin secretions from anuran amphibian species belonging to the families Ascaphidae, Bombinatatoridae, Hylidae, and Ranidae.8,16−27 More than 70 B


name

peptide RD-11 peptide AR-10 peptide AV-12 maximakinin bombinakinin O/kinin O bombinakinin M bombinakinin MV kinestatin ranakinin-N ranakinin RR-10 LR-9 phypo Xa amolopkinin (Arg0, Trp5, Leu8) bradykinin (Hyp3) bradykinin (Val1, Thr6) bradykinin (Val1) bradykinin (Ala3, Thr6) bradykinin (Val1, Thr3, Thr6) bradykinin bradykinin-related peptide neuromedin N-related peptides 1 neuromedin N-related peptides 12 (Leu8) bradykinin-related peptide 1 (Leu8) bradykinin-related peptide 2 (Leu8) bradykinin-related peptide 3 (Leu8) bradykinin-related peptide 4 (Des-Arg9) bradykinin bradykinin-related peptide 1 bradykinin-related peptide 2 bradykinin-related peptide 3 bradykinin-related peptide 4 (Thr6) bradykinin ranakinin R R-13-R (Phe9, Phe12) R-13-R I-11-R

Bradykinins bradykinin

RP RP RP OS, RT, PJ RT RT RT RT BO, LP, HG, PJ RR RC RC RC

IRRPPGFSPLR

AGIRRPPGFSPLR

IRRPPGFSPLRIA

RPPGFSPF LIPIVGRPPGFSPFR RPPGFSPFRIA RPPGFSPFRIAPASTL RPPGFSPFRIAPASIL RPPGFTPFR RPPGFSPFRIAPEIV RVISLPAGLSPLR RVISLPAGFSPFR IRRPPGFSPLR

species

RPPGFSPFRVD APVPGLSPFR APVPGLSPFRVV DLPKINRKGPRPPGFSPFR RPPGFSPFRGKFH DLPKINRKGPRPPGFSPFR DLSKMSFLHGIRPPGFSPFR PEIPGLGPLR-NH2 RAEAVPPGFTPFR RPPGFSPFRVAPAS RLPPGFTPWR LPPGFTPWR FRPSYQIPP RAPVPPGFTPFR RRPPGWSPLR RP(Hyp)GFSPFR VPPGFTPFR VPPGFSPFR RPAGFTPFR VPTGFTPFR RPPGFSPFR KKPYIL HLRRCGKKPYILMACS AGIRRPPGFSPLRIA

sequence BO, HS, AT, HG, LP, RT, RC, OS, PJ AT AT AT BM BO BM BM BM RN OS RS RS PH, PJ AL PKE HG, RT HG HG BV BV RP RP RP RP

RPPGFSPFR

Table 1. Myotropical Peptides from Amphibiansa

C

36, 44, 122 44 44 44 44 16, 21, 26, 122 21 21 21 21

25

25

25

8−11, 16, 21, 23, 26, 36, 44, 122 9 9 9 37 14 28 28 24 35 36 41 41 30, 122 41 38 16, 44 16 16 27 27 25 25 25 25

ref

Chemical Reviews Review


Bradykinins bradykinyl-IAPAS (Thr6) bradykininl-IAPAS (Val1, Thr6) bradykinin Des(Arg9, Thr6) bradykinin phyllokinin desulfonated (Thr6) phyllokinin desulfonated (Thr6) phyllokinin (Hyp3) phyllokinin phyllokinin Bombesins PG-L ranatensin bombesin-RS bombesin-SV bombesin His6-bombesin Phe13-bombesin Asp2, Phe4-SAP-bombesin PR-bombesin bombestatin (Leu13) bombesin (Phe13) bombesin (SAP) bombesin BLP-B1 BLP-B2 BLP-B3 BLP-B4 BLP-B5 GRP-1 GRP-2 neuromedin C bombesin-like peptide 1 bombesin-like peptide 2 bombesin-like peptide 3 litorin Glu(OMe)2 litorin Glu(OEt)2 litorin PG litorin Tachykinins uperolein uperin 1.1 hylambatin

name

Table 1. continued

LP LP LP PJ PJ PJ PJ AC PHY, PJ PG RP RS SV BB, BV BV BV BV BM BM BO BO BO OG OG OG OG OG XL XL XL BV BV BV LA LA UR PG UM, UR UI KM

RPPGFSPFRIAPAS RPPGFTPFRIAPAS VPPGFTPFR RPPGFTPF RPPGFSPFRIY RPPGFTPFRIY RPPGFTPFRIY(SO3) RPHypGFSPFRIY RPPGFSPFRIY(SO3)

QGGGPQWAVGHFM QVPQWAVGHFMG pETSFMAPSWALGHLM-NH2 pEMIFGAPMWALGHLM-NH2 pEQRLGNQWAVGHLM-NH2 pEQRLGHQWAVGHLM-NH2 pEQRLGNQWAVGHFM-NH2 pEDSFGNQWARGHFM-NH2 EKKPPRPPNWAVGHFM-NH2 WEVLLNVALIRLELLSCRSSKDQDQKESCGMHSW EQRLGNQWAVGHLM EQRLGNQWAVGHFM EQSLGNQWARGHFM pEREYRAPHWAIGHFM-NH2 pEREYRTPHWAIGHFM-NH2 pERECRAPHWAIGHFM-NH2 pENTYRAPQWAVGHLM-NH2 pESTYRAPQWAVGHLM-NH2 APTSQQHTEQLSRSNINTRGSHWAVGHLM-NH2 APTSQQHTEQLSRSTINTRGSHWAVGHLM-NH2 GSHWAVGHLM pQRLGHQWAVGHLM pDSFGNQWARGHFM pQRLGNQWAVGHLM pEQWAVGHM-NH2 pEE(OMe)WAVGHM-NH2 pEE(OEt)WAVGHM-NH2 pEGGGPQWAVGHFM-NH2

pEPDPNAFYGLM-NH2 pEADPNAFYGLM-NH2 DPPDPDRFYGMM-NH2

sequence

species

D

77, 123 124 125

61 130 51 52 45, 46, 48 46, 48 46, 48 46, 48 48, 49 47 55 55 55 5 5 5 5 5 56 56 56 54 54 54 123 131 64 61

21 21 21 122 122 122 122 65 45, 122

ref



Tachykinins kassinin (Glu2, Pro5) kassinin phyllomedusin ranatachykinin A ranatachykinin B ranatachykinin C ranatachykinin D physalaemin (Lys5, Thr6) physalaemin ranakinin neurokinin B-related peptide Rranamargarin PG-SPI PG-SPII PG-KI PG-KII PG-KIII bufokinin nurokinin-A Xenopus SP NKA-related peptide tachykinin OG1 AR-1 AR-2 AR-3 AR-4 AL-1 Tryptophyllins PdT-1 PdT-2 PsT-1 tryptophyllin tryptophyllin 13 HaT2 HaTL-1 HaTL-2 HaTL-3 HaTL-4 HaTL-5 tryptophyllin L1 tryptophyllin L2 tryptophyllin L3

name

Table 1. continued

KS KM PB RCA RCA RCA RCA PF UR PR PR OM PG PG PG PG PG BMA RR XL XL OG AC AC AC AC AC PD PD PS PER PER HS HS HS HS HS HS LR LR LR

DVPKSDQFVGLM-NH2 DEPKPDNFVGLM-NH2 QNPNRFIGLM-NH2 KPSPDRFYGLM-NH2 YKSDSFYGLM-NH2 HNPASFIGLM-NH2 KPNPERFYAPM-NH2 QADPNKFYGLM-NH2 pEADPKTFYGLM-NH2 KPNPERFYGLM-NH2 DMHDFFVGLM-NH2 DDASDRAKKFYGLM-NH2 QPNPDEFFGLM-NH2 QPNPNEFFGLM-NH2 pEPHPDEFVGLM-NH2 pEPNPDEFVGLM-NH2 pEPHPNEFVGLM-NH2 KPRPDNFYGLM-NH2 HKLDSFIGLM-NH2 KPRPDNFYGLM-NH2 TLTTGKDFVGLM-NH2 DDTEDLANKFIGLM-NH2 GPPDPNKFIGLM-NH2 GPPDPDR(K)FTPGM-NH2 pEPDPDRFYPGM-NH2 GPPDPNKFYPVM-NH2 GPPDPNKFIGLM-NH2

KPPAWVP-NH2 DMSPPWH-NH2 KPPPWVPV KPPSWIP EEKPYWPPPI YPM FLPWL-NH2 PFW-NH2 IIPFW-NH2 XFPFW-NH2 FXXFWP-NH2 FLPFFP-NH2 FPWL-NH2 pEFPWL-NH2 FLPWY-NH2

sequence

species

E

82 83 84 133 134 80 80 80 80 80 80 135 135 135

70 126 92 67 67 67 67 127 128 13 13 129 61 61 61 61 61 63 132 127 127 75 65 65 65 65 65

ref



Tryptophyllins tryptophyllin L4 tryptophyllin L1.1 tryptophyllin L1.2 tryptophyllin L1.3 tryptophyllin L1.4 tryptophyllin L1.5 tryptophyllin L1.6 tryptophyllin L2.1 tryptophyllin L3.1 tryptophyllin L3.2 tryptophyllin L3.3 tryptophyllin L4.1 tryptophyllin L4.2 tryptophyllin L5.1 tryptophyllin L6.1 rubellidin 1.1 rubellidin 1.2 rubellidin 1.3 rubellidin 1.4 rubellidin unnamed rubellidin unnamed electrin 1 electrin 2 electrin 3 electrin 4 dentatin 1.1 dentatin 1.2 dentatin 1.3 fallaxidin 1.1 fallaxidin 1.2 fallaxidin 1.3 fallaxidin 1.4 peak 7 peak 9 Pj-T3-1 Pj-T3-2 Pj-T3-3 unnamed Pha-T3-1 Pha-T3-2 unnamed GM-14

name

Table 1. continued

pEIPWFHR-NH2 PWL-NH2 FPWL-NH2 pEFPWL-NH2 FPFPWL-NH2 FPKynL-NH2 FP(5-HO-Trp)L-NH2 IPWL-NH2 FPWP-NH2 FPWP pEFPWF-NH2 LPWY-NH2 FLPWY-NH2 pEIPWFHR-NH2 SPWL-NH2 VDFFA IEFFA IEFFT VEFFT LFFWG-NH2 IFFFP-NH2 FVPIYM-NH2 FVHPM FITVH-NH2 IYEPEIA-NH2 WSPFWD-NH2 WSPFWR-NH2 FNPFMI-NH2 YFPIPI-NH2 YFPIPF-NH2 YHPF-NH2 FWPFM-NH2 DPWDWV EPRTPWDWV pDKPFWSPPIYPV pDKPFWSPPIYPH pDKPFWDPPIYPV pDKPFWPPPIYPV pDKPFWPPPIYIM pDKPFWPPPIYPM EKPFYPPPIYPV GKPFYPPPIYPEDM

sequence LR LE, LR LE, LR LE, LR LE, LR LE, LR LE, LR LE, LR LE, LR LE, LR LE, LR LE, LR LE, LR LE, LR LE, LR LE, LR LE, LR LE, LR LE, LR LEW LEW LE, LR LE, LR LE, LR LE, LR LE, LR LE, LR LE, LR LF LF LF LF AT AT PJ PJ PJ PS PA, PS PS PB BV

species 135 136 136 136 136 136 136 136 136 136 136 136 136 136 136 136 136 136 136 137 137 138 138 138 138 136 136 136 139 139 139 139 9 9 122 122 122 122 122 122 122 122

ref


F


caerulein 1.2/Phe8 caerulein caerin 1.10 caerulein 2.1 caerulein 2.2 caerulein 3.1 caerulein 3.2 caerulein 4.1 caerulein 4.2 caerulein1.1 desulfated/caerulein NS caerulein 1.2 desulfated caerulein 2.1 desulfated caerulein 2.2 desulfated caerulein 3.1 desulfated caerulein 3.2 desulfated caerulein 4.1 desulfated caerulein 4.2 desulfated phyllocaerulein (Asn2, Leu5) caer (Glu(OMe)2) caer (Leu3) caerulein (3−10) CPF-7 CPF-SE1 CPF-SE2 CPF-SE3 CPF-5 CPF-3 CPF-6 CPF-1 CPF-PG1 CPF-AM1 caerulein-B1 caerulein-B2 caerulein-B1 desulfated AC-phyllocaerulein (Arg4) phyllocaerulein Cholecystokinins cholecystokinin cholecystokinin-69

Caeruleins caerulein/caerulein 1.1

name

Table 1. continued

LC LC LC LC LC LC LC PS KM RE RE XL SE, XL SE, XL SE, XL XL XL XL XL XP XA XB XB XB AC PJ RN, RCA RCA

pEQDY(SO3)TGWFDF-NH2 GLLSVLGSVAKHVLPHVVPVIAEKL-NH2 pEQDY(SO3)TGAHMDF-NH2 pEQDY(SO3)TGAHFDF-NH2 pEQDY(SO3)GTGWMDF-NH2 pEQDY(SO3)GTGWFDF-NH2 pEQDY(SO3)TGSHMDF-NH2 pEQDY(SO3)TGSHFDF-NH2 pEQDYTGWMDF-NH2

pEQDYTGWFDF-NH2 pEQDYTGAHMDF-NH2 pEQDYTGAHFDF-NH2 pEQDYGTGWMDF-NH2 pEQDYGTGWFDF-NH2 pEQDYTGSHMDF-NH2 pEQDYTGSHFDF-NH2 pEEY(SO3)TGWMDF-NH2 pENDY(SO3)LGWMDF-NH2 pEE(OMe)DY(SO3)TGWMDF-NH2 DY(SO3)LGWMDF-NH2 GFGSFLGKALKAALKIGANALGGAPQQ GFLGPLLKLGLKGVAKVIPHLIPSRQQ GFLGPLLKLGLKGAAKLLPQLLPSRQQ GFLGSLLKTGLKVGSNLL GFGSFLGKALKTALKIGANALGGSPQQ GFGSFLGKALKAALKIGANALGGSPQQ GFASFLGKALKAALKIGANMLGGAPQQ GLASFLGKALKAGLKIGAHLLGGAPQQ GFGSLLGKALKIGTNLL-NH2 GLGSVLGKALKIGANLL-NH2 pEQDY(SO3)GTGWMDF-NH2 pEDY(SO3)TGWMDF-NH2 pEQDYGTGWMDF-NH2 pEDY(SO3)KGWMDF-NH2 pEYRGWMDF-NH2

RVDGNSDQKAVIGAMLAKDLQTRKAGSSTGRYAVLPNRPVIDPTHRINDRDYMGWMDF ASSSAQLKPFQRIDGTSDQKAVIGAMLAKYLQTRKAGSSTGRYAVLPNRPVIDPTHRINDRDY(SO 3) MGWMDF-NH2

species XL, LL, LC, LR, XA, LLE, LP, HC, PS LC, LS, LSU, LR LS LC LC LC LC LC LC LC, LS

pEQDY(SO3)TGWMDF-NH2

sequence

G

113 115

97 97 97 97 97 97 97 93 143 77 77 108 108 108 108 108 108 108 108 105 109 96 96 96 65 122

86, 95, 97, 98 98 97 97 97 97 97 97 97, 98

86, 91−94, 96, 97, 140−142

ref



H

RCA RCA RCA RCA XL XL RCA RCA PP PP KS PS AL XL, XA XA LP LP LP LP LP

TLLCKYFAIC QGGLLGKVSNLANDALGILPI FLPFLIPALTSLISSL-NH2 LRPAILVRTK-NH2 FLPIVGAKL-NH2 pEGKRPWIL pEGRRPWIL pEPWLPFG-NH2 pEPWIPFV-NH2 pEPWLPFV-NH2 pETWLPFV-NH2 pEPWLPFR-NH2

RCA

VPSSAGQLKPIQRLDGNVDQKANIGALLAKYLQQARKGPTGRISMMGNRVQNIDPTHRINDRDY(SO 3) MGWMDF-NH2 YMGWMDF DYMGWMDF RIDGTSDQKAVIGAMLAKYLQTRKAGSSTGRYAVLPNRPVIDPTHRINDRDYMGWMDF GSSTGRYAVLPNRPVIDPTHRINDRDYMGWMDF DYMGWMDF YMGWMDF LLASLTHEQKQLIMSQLLPELLSELSNAEDHLHPMRDRDYAGWMDF QKQLIMSQLLPELLSELSNAEDHLHPMRDRDYAGWMDF

sequence

species

144 119 116 117 120 96, 145 96 142 142 142 142 142

115 115 115 115 112 112 110 114

115

ref

AC, agalychnis callidryas; AL, Amolops loloensis; AT, Ascaphus truei; BB, Bombina bombina; BM, Bombina maxima; BMA, Bufo marinus; BO, Bombina orientalis; BV, Bombina variegata; HG, Hylarana guentheri; HC, Hyla caerulea; HS, Hyla schelkownikowi; KM, Kassina maculata; KS, Kassina senegalensis; LA, Litoria aurea; LC, Litoria citropa; LE, Litoria electrica; LEW, Litoria ewingi; LF, Litoria fallax; LL, Litoria labyrinthicus; LLE, Litoria lesueuri; LP, Lithobates pipiens; LPE, Litoria peronii; LR, Litoria rubella; LRO, Litoria rothii; LS, Litoria splendid; LSU, Litoria subglandulosa; OG, Odorrana graham; OM, Odorrana margaretae; OS, Odorrana schmackeri; PA, Phyllomedusa azurea; PB, Phyllomedusa bicolor; PD, Phyllomedusa dacnicolor; PER, Pelophylax ridibundus; PF, Physalaemus fuscomaculatus; PG, Pseudophryne güntheri; PH, Phyllomedusa hypochondrialis; PHY, Phyllomedusa sp.; PJ, Phasmahyla jandaia; PKE, Pelophylax kl. esculentus; PP, Polypedates pingbianensis; PR, Phyllomedusa rohdei; PS, Phyllomedusa sauvagei; RC, Rana chensinensis; RCA, Rana catesbeiana; RE, Rana erythraea; RN, Rana nigrovittata; RP, Rana palustris; RR, Rana ridibunda; RRU, Rana rugosa; RS, Rana sakuraii; RSH, Rana shuchinae; RT, Rana temporaria; SE, Silurana epitropicalis; SV, Silurana varians; UI, Uperoleia inundata; UM, Uperoleia marmorata; UR, Uperoleia rugosa; XA, Xenopus amieti; XB, Xenopus borealis; XL, Xenopus laevis; XP, Xenopus pygmaeus.

a

cholecystokinin-7 cholecystokinin-8 cholecystokinin-58 cholecystokinin-33 cholecystokinin A cholecystokinin B cholecystokinin-like peptide cholecystokinin homologue Other Myotropical Peptides polypedatein polypedarelaxin 1 senegalin sauvatide amolos xenopsin xenopsin-AM2 peronein 1.1 peronein 1.2 peronein 1.3 peronein 1.4 peronein 1.5

Cholecystokinins cholecystokinin-70

name

Table 1. continued



Chemical Reviews

Review

bombesin > (SAP) bombesin; for the BB2 receptor, potencies are (Leu13) bombesin > (Phe13) bombesin > (SAP) bombesin (5−14) > (SAP) bombesin. None of these peptides has highaffinity binding to the BB3 receptor.55 2.1.3. Tachykinins. Amphibians are a rich source of natural TKs, and more than 28 TK-like peptides have been isolated from amphibian skin, gut, and brain.59−61 Nevertheless, most amphibian TKs with different structures have no mammalian homologues, although bufokinin, ranakinin, and ranatachykinin A, and the amphibian substance P (SP)-related peptides, have been identified as having an N-terminal motif R/KPXP like their mammalian counterpart, SP.62,63 These TKs show a spectrum of biological actions that are usually the same as mammalian TKs. For example, both uperolein and uperin 1.1 display potent vasodilator, hypertensive action, and intense spasmogenic activity toward smooth muscle.64 Like their mammalian counterpart, most amphibian TKs contain the classical C-terminal pentapeptide motif FXGLMNH2 and at least one P residue in the N-terminus. The Cterminal motif is necessary but not sufficient for bioactivity, and the minimum chain length required for activity is 6 residues. In addition, the amidation and F5 residue from the C-terminus are important for bioactivity. Exceptions are that (1) tachykinins AR1, AR2, and AR3 from the skin of the frog Agalychnis callidryas contain the sequence FYPGM-NH2 and tachykinins AR4 from the conspecifics have the sequence FYPVM-NH2 at their C-terminal region;65 (2) hylambatin from the skin of the frog Hylambates maculatus contains FYGMM-NH2 at the Cterminal region;66 and (3) ranatachykinin D has FYAPMNH2.67 The M-NH2 at C-terminus and F5 residue at the Cterminus are immutable in most TKs.68 On the basis of their chemical structure and receptor affinities, TKs from amphibians can be grouped into two subfamilies, aromatic TKs with the C-terminal pentapeptide FY/FGLM-NH2 and aliphatic TKs with the C-terminal pentapeptide FV/IGLM-NH2. V4 or I4 from the C-terminus of amphibian aliphatic TKs is thought to be important for differentiating NKA and NKB-like versus SP-like activity, and some representative aliphatic TKs such as kassinin have less affinity for mammalian NK1 receptors than for NK2 and NK3 receptors.69−72 However, cod SP containing an I8 displays high affinity to a toad NK1-like receptor.73 The aromatic TKs preferentially interact with the mammalian NK1 receptor. Generally, the amidated C-terminal pentapeptide is important for receptor interaction, while the “inactive” N-terminus is important for distinguishing between receptor subtypes and for different biological actions. For example, in CHO cells transfected with the bullfrog SP receptor, the order of TK ability to increase intracellular Ca2+ is RTKA ≥ SP > RTKC ≥ RTKB.74 Additionally, analyses and comparisons of interactions between bufokinin and SP as well as between their C-terminal fragments and bufokinin receptors in the small intestine of the toad B. marinus show that receptor−ligand interactions are favored by basic and rigid residues at positions 1−3 and the conformation at bufokinin N-terminus is important.62,73 Amphibian TKs usually adopt α-helices from the middle region to the C-terminus, which are essential for receptor activation and have great flexibility in the N-terminus. For example, in the sodium dodecyl sulfate (SDS) micelle system, RTKA, RTKB, and RTKC have helix-spanning residues 4−10 with a large degree of flexibility in the N-terminus and minor dynamic fraying at the end of the C-terminus.74

deriviation of BRPs show that many amphibian skin BRPs also exist in their putative predators. For instance, (Arg0, Trp5, Leu8) bradykinin from the skin secretion of the frog Pelophylax kl. esculentus has been reported in plasma kininogens of bony fish hunting the former.38 The (Val1, Thr6) bradykinin in the skin secretions of many phyllomedusines and ranids can be found in their common predators, colubrid snakes.39 Some BKs have been isolated from Hylarana guentheri and its vertebrate predators, which coexist in H. guentheri habitats.16,40 Amphibian skin BRPs are obviously structural homologues, and an intriguing phenomenon is that all skin prepro-BKs or BRP precursors contain a highly conserved signal peptide with one or more acidic spacer fragments and one or more tandem copies of single or multiple mature BRPs. These structural characteristics are typical of defensive peptide precursors from amphibian skins.8,16,21−27,36,37,41 Finally, some BRPs, like maximakinin from B. maxima skin secretions, display highly receptor subtype specificity against different predators that are enhanced by N-terminal extensions resulting from molecular evolution.42 Nevertheless, metabolites of maximakinin produced by incubation with mammalian kallikrein and salivary proteases have greater potency than the original maximakinin but the same discrete tissue and/or receptor selectivity. These results show that maximakinin is resistant to proteases and an efficient defensive weapon for toads against predators.43,44 2.1.2. Bombesins. Since first isolation of bombesin from the skin of B. bombina in 1971,45 more than 30 bombesins and related peptides have been isolated from amphibian skin (Table 1). In amphibians, these peptides are divided into three distinct subfamilies according to their common structural features and to a lesser extent, pharmacological actions: bombesins, ranatensins, and phyllolitorins. Each subfamily is characterized by common aa near the C-terminus. Bombesins have an L as the penultimate residue; ranatensins have an F as the penultimate residue; phyllolitorins have an S as the third residue from the C-terminus.46−49 Bombesin mediates a variety of biological activities in the central nervous system and gastrointestinal tract of amphibians including contracting smooth muscle, stimulating or suppressing gastrointestinal secretion, causing potent antidiuretic effects, and regulating central homeostatic mechanisms.50 These potent pharmacological properties make bombesins efficient defensive agents against predators, especially because the major predators of frogs are other vertebrates, for example, snakes, birds, or mammals. Bombesin-RS, bombesin-SV, bombestatin, bombesin, Phe13-bombesin, His6-bombesin, and Asp2, Phe4-SAPbombesin elicit concentration-dependent contractions of urinary bladder smooth muscle, or rat stomach strip or uterus smooth muscle.46,47,51−55 Synthetic GRP-1 produces concentration-dependent contractile effects on lengthwise smooth muscle strips from Xenopus cardiac stomach and concentrationdependent relaxation of precontracted circular smooth muscle strips from the same region.56 Bombesins mediate their physiological functions through typical G-protein-coupled BB1, BB2, and BB3 receptors, which are expressed in many mammalian tissues such as brain, the gastrointestinal tract, and the central nervous system.57,58 Different bombesins show different receptor interactions. For example, the frog B. orientalis has three distinct bombesin forms, each of which is an agonist with different affinity for BB1 and BB2 receptors. Relative potencies for the BB1 receptor are (Phe13) bombesin > (SAP) bombesin (5−14) > (Leu13) I


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exist even in a single amphibian species: 16 caerulein-type peptides from L. citropa belong to 4 groups. Caerulein 1 peptides have 10 aa and caeruleins 2−4 have 11 residues.97 Caerulein expression profiles for some species of tree frog are reported to change with seasons. L. splendida caerulein is a unique peptide with smooth muscle activity in the summer. In the southern winter, caerulein is partially hydrolyzed to the less active desulfated caerulein NS and Phe8 caerulein, which are major components.95,98 Another example is from the tree frog L. rothii. In the summer, caerulein 1.1 is the major smooth muscle active component in the dorsal granular glands of both male and female frogs, and caerulein 1.2 is a minor component. In the winter, caerulein 1.1 is present in only trace amounts, and caerulein 1.2 and rothein 1 are the major peptide components of glandular skin secretions.95,99 Peptides expression changes with seasons are also observed in L. citropa and L. subglandulosa.97,99 Both species secrete caerulein 1.1, 2.1, 3.1, and 4.1 containing M8 in the spring. In the inactive season, these caeruleins are partially hydrolyzed to the desulfated forms, desulfated caeruleins 1.2, 2.2, 3.2, and 4.2. Caeruleins 1 show potent smooth muscle activity comparable to the activity of CCK-8. Caerulein 1.2 is less active with only about 50% of the activity of caerulein 1.1.77 Caeruleins 2, 3, and 4 probably have potent smooth muscle activity, although no experimental evidence for this activity exists. Why these animals generate such a wide spectrum of caeruleins is not clear. Research on cDNAs sequences from X. laevis skin shows that different genes at least in part encode multiple preprocaeruleins that are modified to form caerulein and caerulein precursor fragment (CPF) peptides after translation.100−102 Four different preprocaerulein cDNAs have different number caeruleins copies in their sequence. Similarly, mass spectrometry analysis has identified multiple structurally similar CPF peptides in X. laevis skin secretions.103,104 Multiple CPF peptides have also been reported in skin secretions of Silurana epitropicalis and Xenopus frogs such as X. borealis, X. petersii, X. pygmaeus, X. amieti, X. andrei, X. clivii, and X. lenduensis.105 The CPF peptides generally show broad-spectrum antimicrobial activities and relatively low hemolytic activities.106,107 In addition, some CPF peptides have other activities. For example, CPF-1, CPF-3, CPF-5−7 from X. laevis potently induce insulin release, and CPF-AM1 significantly stimulates GLP-1 release and insulin secretion.108,109 2.1.6. Cholecystokinins. CCKs are important intestinal hormones and neurotransmitters that regulate or affect pancreatic enzyme secretion, gastrointestinal motility, pain hypersensitivity, and digestion and satiety.110,111 Currently, CCKs, which generally contain DYMGWMDFG at the Cterminus, have been extensively reported in mammals but in only H. nigrovittata, X. laevis, and R. catesbeiana.110−113 Two cDNA sequences from X. laevis encoding presentative CCK precursors differ from each other only at a few base pairs, while the regions encoding DYMGWMDFG are identical, indicating that they probably originated from separate genes evolving independently after genome duplication. Two groups of CCKs have been identified from the brain and small intestine of the bullfrog R. catesbeiana using antiserum specific for the common C-terminus of mammalian gastrin and CCK. The group of small peptides contains CCK-7 and CCK-8 and another group contains CCK-69 and CCK-70, which contain Y sulfated at the seventh-to-last residue and are highly identical to each other and to mammalian CCKs. Both CCK-69 and CCK-70 contain the monobasic and dibasic cleavage sites that give rise to CCK-

Although a large number of TKs have been identified from amphibians, only one amphibian TK precursor has been identified, from Odorrana grahami. The precursor encoding the amphibian TK contains 61 aa with a signal peptide followed by an acidic spacer peptide and one copy of a mature TK-like peptide that is different in number of residues and copies from the human and ascidian proTKs.75 2.1.4. Tryptophyllins. TPHs other than TPH-13 generally contain a common W2 residue from the C-terminus and 1 or 2 P residues at positions 2 and 3 from the N-terminus.76 TPHs are a heterogeneous group that are described solely according to chemical structure rather than by bioactivity, have no counterparts in mammals, and are different from other peptide groups from amphibian skin secretions.77 These peptides were first isolated from methanol extracts of P. rohdei skin.78 A number of TPHs have since been discovered from the skins of frogs from the family Hylidae, predominantly from the genera Phyllomedusa and Litoria (Table 1).76,79 In 2005, research on TPHs from the skin secretions of the extant frogs Ascaphus truei showed TPH-encoding genes in the early stages of amphibian evolution.9 In 2010, several TPHs and related peptides were found in the leaf frog Hyla arborea schelkownikowi and the tree frog H. savignyi.80,81 To date, over 40 TPHs belonging to T-1, T-2, and T-3 groups have been found in frog skin secretions (Table 1). T-1 TPHs are heptapeptides or octapeptides exemplified by PdT-1, which has N-terminal basic aa residues and an internal PW or PPW sequence. The most heterogeneous group, T-2 TPHs, contains an internal PW doublet, amidated C-terminus, and a different number of aa residues. T3 TPHs are the most highly conserved group and are tridecapeptides with an internal PPPIYP motif. PdT-1 and PdT-2 from the skin of Pachymedusa dacnicolor have strong myotropic activity.82,83 PsT-1 from P. sauvagei, a homologue of PdT-1 and PdT-2, inhibits BK-induced vasodilatation of phenylephrine preconstricted rat tail artery smooth muscle and proliferation of three human prostate cancer cell lines. These results indicate that PsT-1 is likely a BK receptor antagonist.84 Peptides with the sequence FPPWM-NH2 also appear in a set of cells in the rat adenohypophysis and sedate birds and induce sleep.76 However, most T-2 and all T-3 TPHs are inactive in bioassays with arterial, intestinal urinary bladder, and gall bladder smooth muscles.78,82,85−87 2.1.5. Caeruleins. Caeruleins are one of the most heavily researched pharmacological amphibian peptides. Their bioactivities are highly alike mammalian gastrin and CCK, which acts via CCK1 and CCK2 receptors.77 Caeruleins have smooth muscle activity and analgesic properties and influence or regulate body temperature, blood pressure, food intake, the hibernation cycle of anurans, and Na+ absorption and release through amphibian skin.77,88−90 The amphibian skin peptide caerulein was first isolated from H. caerulea and subsequently from X. lavis, Leptodactylus labrinthinicus, and P. sauvagei.91−93 At present, caeruleins and caerulein-like peptides have been found in the skins of X. borealis, X. amieti, H. erythraea, Kassina maculata, L. pentadactylus, and multiple species in the genera Hyla, Litoria, and Phyllomedusa.94−96 Although the N-terminal aa sequences of the caeruleins vary, the C-terminal region of most caeruleins from amphibians is conserved and contains GWMDF-NH2, which is common to the mammalian CCK and gastrin. Some modification occurs in the aa sequences of caeruleins. For example, AC-phyllocaerulein, a caerulein from the skin of A. callidryas, contains a sulfated Y residue that is crucial for peripheral biologic activity.65 Multiple caeruleins J


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Table 2. Naturally Occurring Amphibian Dermorphinsa name

sequence

species

ref

dermorphin dermorphin [Hyp6] dermorphin [Lys7-NH2] dermorphin [Lys7-OH] dermorphin [Trp4-NH2] dermorphin [Trp4, Asn5] dermorphin [Trp4-OH] dermorphin [Trp4, Asn7-NH2] dermorphin [Trp4, Asn7-OH] dermorphin [Trp4, Asn5-OH] dermorphin Y10A Y131

YAFGYPS-NH2 Y(D-Ala)FGYPS-NH2 Y(D-Ala)FGY(HypS)-NH2 Y(D-Ala)FGYPK-NH2 Y(D-Ala)FGYPK Y(D-Ala)FWYPS-NH2 Y(D-Ala)FWN-NH2 Y(D-Ala)FWN Y(D-Ala)FWYPN-NH2 Y(D-Ala)FWYPN Y(D-Ala)FWN Y(D-Ala)FGYPSGEA Y(D-Ala)FGYPSGEAKKI

PJ, PR AC, PJ, PS, PB, PBU, PR, PH, PT AC, PJ, PS, PB, PBU, PR, PH, PT PB PB PB PB PB PB PB PB PS PS

122, 154 65, 149, 153, 155 65, 149, 153, 155 156 157 156 156 156 156 157 158 153 153

a

AC, Agalychnis callidryas; PB, Phyllomedusa bicolor; PBU, Phyllomedusa burmeisteri; PH, Phyllomedusa hypochondrialis; PJ, Phasmahyla jandaia; PR, Phyllomedusa rohdei; PS, Phyllomedusa sauvagei; PT, Phyllomedusa tarsius.

Table 3. Naturally Occurring Amphibian Deltorphins name

sequence

species

ref

DMet-deltorphin/dermenkephalin/deltorphin DAla-deltorphin I DAla-deltorphin II Dlle-deltorphin DLeu-deltorphin-17 [Met(Ox)]6-deltorphin deltorphin

Y(D-Met)FHLMD-NH2 Y(D-Ala)FDVVG-NH2 Y(D-Ala)FEVVG Y(D-Ile)FHLMD-NH2 Y(D-Leu)FADVASTIGDFFHSI-NH2 YMFHLMoxD-NH2 YAFGYPS-NH2

PB, PBU, PJ, PR, PS PB, PBU, PR, PS, PT PB AA, PD PBU PJ PJ

122, 149, 153, 155, 160, 158, 161 158, 161 162 163 122 122

33, CCK-39, and CCK-58 in mammals.114,115 In addition, a CCK isoform has been also identified from the skin secretions of H. nigrovittata.113 2.1.7. Other Myotropical Peptides. Recently, polypedatein, polypedarelaxin 1, sauvatide, and senegalin have been reported to affect contraction of isolated ileums and rat urinary bladder smooth muscle. These peptides belong to novel peptide families according to their primary structures. Conserved structural motifs exist in known amphibian myotropical peptides such as BKs, bombesins, CCKs, and TKs. However, polypedatein, polypedarelaxin 1, sauvatide, and senegalin do not contain these structural features, suggesting that they cannot be classified into these peptide families. Precursors of these precursors display the typical domain organization of amphibian skin peptide precursors with signal peptides that have marked sequence similarity to other amphibian skin defensive peptides including BKs, TKs, lectins, serine protease inhibitors, AMPs, and opioid peptides. These findings suggest that these peptides belong to defensive peptide groups. Polypedatein, polypedarelaxin 1, sauvatide, and senegalin thus represent prototypes of amphibian skin bioactive peptides and illustrate that amphibian skin secretions are unique sources of novel and potent biologically active peptides acting through functional targets in mammalian tissues.116−120 Xenopsin from skin of X. laevis displays partial structural similarity to the C-terminal fragment of the mammalian peptide neurotensin (GKRPYIL) and affects gastrointestinal smooth muscle contractions of the guinea pig esophagus and spontaneous transverse contractions of porcine distal jejunum.121 Amolos from the skin of the frog Amolops loloensis enhance the nociceptive responses caused by inflammation factors and inhibits ileum contraction.120 The peronein peptides are major constituents in skin secretions of the tree

frog L. peronii, and peroneins 1.1, 1.2, and 1.4 display moderate smooth muscle activity at 10−7 M. However, unlike other myotropical peptides discussed in this section, the receptor through which they act is not clear. Frogs secrete caerulein, which has much greater smooth muscle activity. The reason they secrete the other myotropical peptide is not known.86 2.2. Opioid Peptides

Opioid-like peptides are analgesics and have behavioral effects such as dependence and tolerance through some receptors. Since the first skin opioid peptide was discovered in Amazonian frogs in the1980s,77 more than 20 amphibian opioid peptides have been identified from the skin of species belonging to genera Phyllomedusa, Agalychnis, Phasmahyla, and Pachymedusa (Tables 2 and 3). These amphibian skin opioid peptides contain generally the motif Y-DXaa-F at the N-terminus, which is essential for opiate-receptor binding. Yl and F3 are of Lconfiguration, and X2aa is a D-aa derived from posttranslational reaction of a quantitative inversion of the chirality of the αcarbon of the L-aa residue of the precursor.146−149 Similar to mammalian prohormones, all opioid peptides precursors from amphibian skins contain an extra C-terminal G residue flanked by KR, which is necessary for the carboxamidation of the mature heptapeptide. On the basis of the selectivity of their Cterminal domain for the μ- and δ-opioid receptors, amphibian opioid peptides with this motif are grouped into the dermorphin and deltorphin subfamilies. In addition, some classical mammalian-like opioid peptides containing the common N-terminal sequence YGGF without C-terminal amidation have been identified from X. laevis and B. marinus.150−152 Some peptides such as tryptophyllins, amolos, and odorranaopin, which do not have the two opiate peptide motifs or bind to other receptors, also have an analgesic effect.32,120 K


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Table 4. Corticotropin-Releasing Peptides from Amphibiansa name

sequence

species

ref

CRH NVRP-1 NVRP-2 NVRP-3 NVRP-4 PS-sauvagine PD-sauvagine CRF CRH CRF CRF urotensin II urocortin I urocortin III

SEEPPISLDLTFHLLREVLEMARAEQIAQQAHSNRKLMD HSDAVFTDNYSRLLGKTALKNYLDGALKKE HSDAVFTDNYSRLLAKTALKNYLDGALKKE HSDAVFTDNYSRLLGKIALKNYLDEALKKE SDAVFTDNYSRLLGKTALKNYLDSALKKE QGPPISIDLSLELLRKMIEIEKQEKEKQQAANNRLLLDTI pQGTSLDLTFDLLRHNLEIAKQEALKKQAAKNRLLLDTI EEPPISLDLTFHLLREVLEMARAEQIAQQAHSNRKLMDII EEPPISLDLTFHLLREVLEMARAEQIAQQAHSNRKLMDII EPPISLDLTFHLLREVLEMARAEQIAQQAHSNRKLMD EEPPISLDLTFHLLREVLEMARAEQIAQQAHSNRKLMDII AGNLSECFWKYCV EDPPISIDLTFHILRQMIEIAKTQNQKQQAEQNRIIFDSV TKFTLSLDVPTNLMNILFDIAKAKNIRAKAAANAQLMAQI

RCA, RE CP CP CP CP PS PD XL SH RCA PS RR XL XL

176 177 177 177 177 154 174 170, 172, 178 179 173 180 181 169, 175 154, 182

a CP, Cynops pyrrhogaster; PD, Pachymedusa dacnicolor; PS, Phyllomedusa sauvagei; RCA, Rana catesbeiana; RE, Rana erythraea; RR, Rana ridibunda; SH, Scaphiopus hammondii; XL, Xenopus laevis.

phins. Tryptophyllins L1.2 and 3.1 are opioids at 10−7 M that act through the μ-opioid receptor.164 Tryptophyllin L1.3 shows no opioid or smooth muscle activity even though it is a main component of the skin glands of L. dentata, L. electrica, and L. rubella. An analog of tryptophyllins L1.2, FPKynL-NH2 that is a distinctive kynurenine-containing opioid tetrapeptide, has been found in the red tree frog L. rubella. The kynurenine might be derived from direct oxidation of W residue or posttranslational modification. This peptide also exerts opioid activity at 10−7 M, possibly acting through the μ-opioid receptor.136,164 The adenoregulin peptide has opioid activity and has been characterized from the skin of the frog P. bicolor. The sequence of adenoregulin is GLWSKIKEVGKEAAKAAAKAAGKAAL GAVSEAV, which is identical to dermaseptin B2.148,165 Adenoregulin can increase binding of agonists to Al adenosine receptors. Natural adenoregulin has higher activity than synthetic substitutions due to one or more D-aa residues in the natural peptide.165

2.2.1. Dermorphins. A few positively charged dermorphinlike peptides have high μ-opioid receptor selectivity and have been characterized from skin of the frogs A. callidryas, P. jandaia, P. sauvagei, P. burmeisteri, P. rohdei, P. hypohchondrialis, P. tarsius, and P. burmeisteri (Table 2). According to cDNAs of the μ-receptor protein of rodent and human genes, negatively charged residues D114, D147 in putative transmembrane domains II and III are important for ligand binding. This finding may explain the receptor selectivity of dermorphin-like peptides. It also explains why the affinity and selectivity of DAMGO for μopiate receptors of rat brain membranes is 10 times lower than that of [Lys7-NH2] dermorphin. In addition, the finding explains why the μ-receptor affinity of amidated dermorphins is 30−100 times higher than the nonamidated natural dermorphins, which have far less activity on isolated organ preparations, and the reason that the affinity and selectivity of [Lys7-NH2] dermorphin for μ-opiate receptors of rat brain membranes is 10 times higher than DAMGO. Finally, [Lys7NH2] dermorphin and [Trp4, Asn7-NH2] dermorphin have different receptor selectivity, with [Lys7-NH2] binding preferentially to μ1-receptor and [Trp4, Asn7-NH2] dermorphin binding preferentially to μ2-receptor with high affinity. However, [Trp4, Asn7-NH2] dermorphin more potently inhibits electrically stimulated contractions of guinea pig ileum than does [Lys7-NH2] dermorphin.153 2.2.2. Deltorphins. A few negatively charged deltorphins with high δ-opioid receptor selectivity have been characterized from skin of the frog P. bicolor. Electrostatic interactions between deltorphins and δ-opioid receptor are responsible for their receptor selectivity. The grade order of selectivity of Aladeltorphin-I, Ala-deltorphin-II, DLeu-deltorphin-17, Ile-deltorphin, and deltorphin is consistent with their negative values of their charge at the N-terminus and decreases in sequence.159 In addition, the negatively charged C-terminus of DAla-deltorphin II comes into close contact with the positively charged Nterminal Y-DAla-F, folding the backbone into a tight structure that might be preferred by the δ-opiate receptor. 159 Substitution of G4 allows Ala-deltorphins to present a more extended conformation, substantially enhancing their μ-affinity and potency.154 2.2.3. Other Peptides with Analgesic Functions. Tryptophyllins L1.2, 1.3, and 3.1 from the skin glands of L. rubella show sequence identity with human brain endomor-

2.3. Corticotropin-Releasing Peptides

Peptides with functions similar to those of corticotropinreleasing factor (CRF) have been identified from the skins of amphibians such as X. laevis, P. ridibundus, P. sauvagii, R. esculenta, R. catesbeiana, R. sylvatica, L. pipiens, Spea hammondii, and P. dacnicolor (Table 4). Most belong to the CRF family comprising CRF, sauvagine, urocortin/urotensin (UCN I), UCN II, and III, which are probably derived from an ancestral peptide.166−168 Members of the CRF family are expressed in the central nervous system and peripheral tissues where they coordinate and regulate endocrine, autonomic, behavioral, immune, and visceral responses to stress.169 In amphibian tadpoles, CRF-like peptides stimulate release of α-melanocytestimulating hormone (α-MSH), adrenocorticotropic hormone, and β-endorphin from the pituitary gland; they modulate the rate of metamorphosis, control locomotion and appetite, and act as a stress neuropeptide and cytoprotective agent.168,170,171 The receptors and binding proteins of CRF-like peptides are different in amphibians. As compared to UCN I, which has low affinity for the CRF-binding protein, CRF has higher affinity to bind and activate the CRF1 receptor. Although UCN III does not bind CRF-binding protein, it has CRF 2 receptor selectivity.169 A 41-aa mature peptide similar to CRF encoded by two CRF genes from X. laevis is strikingly conserved and differs from rat/ L


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human CRF in only three positions, yet has only 50% homology with sauvagine.172 A gene encoding a CRF homologue is also found in R. catesbeiana. Its mature peptide is named fCRF, and identity is 98% with Xenopus CRF, 95% with human, and 83% with ovine. The potency of fCRF for releasing thyrotropin stimulating hormone (TSH) is almost equivalent to that of ovine CRF. On the basis of that this TSHreleasing activity can be partially inhibited by the CRF-R2 antagonist, CRF-R2 is involved in the CRF-induced TSH release in the bullfrogs.173 The linear amphibian skin peptide of 40 aa from the skin of P. sauvagei, sauvagine, is the first described member of CRF family.154 Sauvagine is highly identical in sequence to CRF from ovine and UCN I from bony fish urophyses.168 A sauvagine homologue is PD-sauvagine, which is identified from P. dacnicolor and has the prolyl residue doublet identified in the N-terminal region of sauvagine and many CRFs.174 The mature PD-sauvagine possesses residue A instead of E occupying this position in sauvagine. The residue A is present in all known CRFs and critical for CRF-binding protein.167,174 Sauvagine can induce a hypotensive action within the cardiovascular system and endogenous responses to stress, stimulate the release of βendorphin and corticotropin, and inhibit the release of growth hormone, prolactin, and thyrotropin.154 Both sauvagine and PD-sauvagine are agonists of endogenous CRF receptors.174 Two urocortins are identified from X. laevis, which are respectively the ortholog of mammalian/fish UCN I and III.169 The deduced mature UCN I from X. laevis is a 40-aa peptide and shows 50% sequence similarity to sauvagine. The deduced X. laevis mature UCN III sequence is highly similar to UCN III from other vertebrates with 90% sequence identity to mouse UCN III but only 27.8% sequence similarity with sauvagine. In X. laevis, UCN I released from neurohemal axon terminals in the pituitary neural lobe functions within the brain as a neurotransmitter/neuromodulator and as a stimulatory neurohormone for α-MSH from neuroendocrine melanotrope cells.175

NO also affects the regulation of water uptake at the pelvic patch of R. catesbeiana, under empty-bladder conditions, through ANG II. Injection of ANG II stimulates an increase in water uptake at the pelvic patch by 23%, and this change correlates with an increase in vascular resistance and mean arterial pressure in the sciatic artery. Inhibition of NO synthase enhances ANG II constriction of aortic rings from frogs. However, in whole-animal studies, inhibition of NO before angiotensin II injection does not enhance water uptake.185 The ANG II and ANG I metabolites and angiotensin 1−7 increase the quantal content at frog neuromuscular junctions through angiotensin receptors involved in presynaptic modulation.186,187 ANG II inhibits NBCe1 current and surface expression in X. laevis oocytes by stimulating internalization of NBCe1 in a protein kinase C-dependent and Ca2+dependent manner.188 Plasma concentrations of ALDO and ANG II in B. marinus are significantly correlated because ANG II regulates blood flow to regions of the body associated with water gain and water loss, stimulating water-absorption behavior in amphibians.189−191 Crinia angiotensin II, which has an extra APG at the N-terminus as compared to human angiotensin II, regulates plasma volume, blood pressure, thirst responses, sympathetic nervous activity, and muscle contraction by activating intracellular signaling cascades through G-protein coupled receptors.77,192 2.5. Protease Inhibitor Peptides

Many protease inhibitor peptides smaller than 10 kDa have been identified from amphibian skins (Table 6). These include bifunctional peptides with both protease-inhibitory and antimicrobial functions such as the ranacyclin-B peptides identified from Ranidae frogs, KPHTI from Kaloula pulchra hainana, HV-BBI from Huia versabilis, HJTI from O. hejiangensis, hylaserpin S2 from H. simplex, OGTI from O. grahami, PYR from R. sevosa, PSKP-1 and PSKP-2 from P. sauvagii, BOTI from B. orientalis, BVTI from B. variegata, BMTI from B. maxima, BPTI from Dyscophus guineti, pLR from L. pipiens, and BSTI from B. bombina.33,196−207 Protease inhibitor peptides are categorized broadly based on structural motifs or the protease inhibited. Using the presence of a defined structural motif, these peptides can be classified into Kunitz, Kasal, and Bowman−Birk classes; by inhibited protease, they are classified into cystatins, serpins, and tissue inhibitors of metalloproteases.198,208 2.5.1. ORB Family. Members of the ORB family such as pLR, pYR, HV-BBI, and ranacyclin-B-like peptides are identified as Bowman−Birk-like trypsin inhibitors. They share a highly conserved precursor structure of 65−70 aa, including a highly conserved N-terminal signal peptide before an acidic aarich domain and a mature peptide domain located at the Cterminus.196,198,201,206 Comparisons of mature peptide sequences show that they have a conserved GCWTKSXXPKPC motif (Table 6).196 Although ORB family members have a similar structure, their bioactivities are quite different. Peptides such as pLR and pYR have immunomodulatory functions.201,206 Ranacyclin-B-like peptides are reported to have antimicrobial and trypsininhibitory activities. Unlike the conservative 9-residue inhibition reactive loop in BBI (CTP1SXPPQC, where P1 represents the residue determining inhibitor specificity), ORB family members have an 11-residue loop (CWTKP1SXXPKPC, the P1 residue is K), with two additional W residues at P3 and P at P6. Because of their different structure, especially the aa differences in the

2.4. Angiotensins

Angiotensin (ANG) exists universally in vertebrates and plays key roles in physiology. The sequence HPF as residues 6−8 at the N-terminus of ANG is generally conserved among species.183 Since the first amphibian ANG was identified in R. catesbeiana, several ANGs and their related peptides have been discovered in Amphiuma tridactylum, Crinia georgiana, Ambystoma mexicanum, and X. laevis (Table 5). Generally, Table 5. Angiotensins from Amphibians name

sequence

species/ref

angiotensin I [Asn1,Val5]angiotensin II [Asp1,Val5]angiotensin II crinia angiotensin II [Asp1, Val5, His9] ANG I angiotensin

DRVYVHPFNL NRVYVHPF DRVYVHPF APGDRIYVHPF DRVYVHPFHL NRVYIHPFNL

R. catesbeiana193 A. tridactylum194 A. tridactylum194 C. georgiana192 A. mexicanum183 X. laevis183,195

most tetrapods studied have [Asp1] ANG, except that the X. laevis and C. georgiana genes encode, respectively, [Asn1] ANG and [Ala1] ANG.183,192 Generally, [Asn1] ANG is more potent than [Asp1] peptides. Like their mammal counterparts, ANGs from amphibian have various bioactivities. ANG II produces a contractile response in isolated toad B. arenarum aortic rings and is regulated by the nitric oxide (NO) system in the toad.184 M


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Table 6. Sequence Comparison of ORB Family name

sequence

ranacyclin B1 ranacyclin B2 ranacyclin B3 ranacyclin B4 ranacyclin B5 ranacyclin-B-RN1 ranacyclin-B-RN2 ranacyclin-B-RN3 ranacyclin-B-RN4 ranacyclin-B-RN5 ranacyclin-B-RN6 ranacyclin-B-RL1 ranacyclin-B-LK1 ranacyclin-B-LK2 ranacyclin-B-AK3 ranacyclin-B-AL1 pLR pYR

AALKGCWTKSIPPKPCFGKR AALKGCWTKSIPPKPCFRKR AALKGCWTKSIPPKPCSGKR AALKGCWTNSIPPKPCSGKR AALRGCWTKSIPPKPCSGKR SALVGCWTKSYPPKPCFGR SALVGCGTKSYPPKPCFGR SALVGCWTKSYPPKPVSVDDKTCLANHLMWNIIWLNARCLMKK SALVGCWTKSYPPKPCFGRG SALVGCWTKSYPPKPCIGRG SALVGCWTKSYPPNPCFGRG AALRGCWTKSIPPKPCPGKR SALVGCWTKSWPPKPCFGRG SALVGCWTKSWPPKPCFGR SMLVGCWTKSYPPKPCFGRG AAFRGCWTKNYSPKPCL LVRGCWTKSYPPKPCFVRG YLKGCWTKSYPPKPCFSR

primary structures, ORB family members probably have different proteinase inhibitory activities and antimicrobial abilities. This may be explained by species adaptation to different environments.196,209 2.5.2. Kunitz/Bovine Pancreatic Trypsin Inhibitor (BPTI) Family. Kunitz inhibitors typically contain about 57− 60 aa, among which 6 C residues form a featured pattern of three disulfide bonds.205 Kunitz inhibitors share a conserved Kazal pattern: -----C-------CBZXXXXXCXXXXXXYXXXC XXC--------------------C (where X is any aa and - is a gap). A few members of the BPTI family have been discovered in amphibian skins including BSTI, BMTI, BOTI, BVTI, PSKP-1, PSKP-2, and KSCI.202−204,207,210 Unlike BBI family peptides, the Kunitz inhibitor family has no overall conservation of aa. However, many studies have found that the interactive domains (positions 12−18 and 34− 39), which interact directly with the protease, are highly conserved. In addition, the secondary structural organization of Kunitz inhibitory proteins is remarkably similar, with three positionally conserved domains of two centrally located βstrands and one C-terminal α-helix. Thus, despite the limited degree of primary structural identity between Kunitz proteins, the scaffold provided by this sequence is apparently capable of maintaining a secondary structure and associated biological activities. PSKP-1 and PSKP-2 isolated from the skin secretions of P. sauvagii have molecular masses of 6.7 and 6.6 kDa, respectively. Unlike other members of the Kazal inhibitors, which all have P at P2, PSKP-1 and PSKP-2 share P both at the P1 and P2 positions. PSKP-1 inhibits serum prolyl endopeptidase, but not trypsin. If P1, P4, P5, and P6 in PSKP-1 are replaced with K and the corresponding residues of acrosin inhibitor, PSKP-1 also inhibits trypsin.202 These findings show that aa residues at certain sites can determine enzyme inhibitor function. BSTI, BMTI, BVTI, and BOTI have been identified from Bombina toad skins. These peptides are 60 residues with 10 C in their sequences. All share structural identity in both nucletide acid and aa sequences and contain a conserved reactive site sequence of CDKKC. The KK doublet is the reaction center of the inhibitor.201,202,204,207

A novel BPTI family peptide with a molecular weight of 6.3 kDa has been identified from skin secretions of the tomato frog D. guineti.205 KPHTI, a trypsin inhibitor identified from K. pulchra hainana skin, is a single chain glycoprotein of 23 kDa by SDS-PAGE that contains the N-terminal sequence DHEVTS. The trypsin inhibitory activity of KPHTI is as potent as the activity of BMTI from B. maxima and BSTI from B. bombina.207 KPHTI contains a stable antitryptic activity in a natural environment and is insensitive to pH range and temperature.197,207 2.5.3. The Biological Roles of Proteinase Inhibitory Peptides in Amphibian Skins. Presently, the biological role of proteinase inhibitory peptides in amphibian skins is explained mainly by two hypotheses. One is that several enzymes are involved in peptide precursor processing or peptide degradation in the skin and proteinase inhibitors negatively modulate the activity of these proteases to avoid premature degradation or release of skin peptides.207 The other hypothesis is that the peptides are surface anti-infective agent similar to AMPs because they inhibit extracellular proteases produced by invading bacteria.205 2.6. Neuropeptides

Neuropeptides in glandular secretions often have host−defense functions and are a necessary part of the defense system that also regulates dermal physiological action.1,77 Studies on the structure−function relationships of peptides in secretions from many frog species have discovered different families of peptides with structural analogs in vertebrate neuroendocrine systems; these include peptide YY, neuromedin U, Bv8, anntoxin, and levitide.1,211,212 Furthermore, the majority of amphibians have at least one neuropeptide in their glandular secretions (Table 7). Active peptides that function as neuropeptides such as some myotropical peptides and angiotensins are described separately above. 2.6.1. FMRFamide Peptides. RFamide peptides from amphibians generally possess the RF-NH2 motif at their Cterminus and were found by stimulation of the molluscan neuropeptide FMRFamide in the ganglia of the venus clam.213 RFamide peptides are important in the nervous and endocrine systems as neurotransmitters and neuromodulators controlling behavioral and physiological processes such as sensory, N


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Table 7. Neuropeptides from Amphibiansa name

sequence

functiona

speciesb/ref

neuromedin U Bm-NmU-17 NmU-23 NPY PYY PP NPY I NPY II PYY I PYY II PP I PP II SPYY PP PP PP PP PP PP NPY NPY NPY PYY signiferin 1 riparin 1.1 riparin 1.2 riparin 1.3 riparin 1.4 riparin 1.5 rothein 1 rothein 1.1 rothein 1.2 IF-8 amide EF-10 amide R-Rfa fGRP fGRP-RP-1 fGRP-RP-2 fGRP-RP-3 GHRP peronein 1.1 peronein 1.2 peronein 1.3 peronein 1.4 peronein 1.5 caerulein 1.1 lesueurin levitide xenoxin-1 xenoxin-2 xenoxin-3 anntoxin anntoxin-S1 anntoxin-S2

LKPDEELQGPGGVLSRGYFVFRPRN DSSGIVGRPFFLFRPRN-NH2 SDEEVQVPGGVISNGYFLFRPRN-NH2 YPSKPDNPGEDAPAEDMAKYYSALRHYINLITRQRY-NH2 YPTKPENPGNDASPEEMAKYLTALRHYINLVTRQRY-NH2 APSEPMHPGDQASPEQLAKYYDDWWQYITFITRPXX YPSKPDNPGEDAPAEDMAKYYSALRHYINLITRQRY-NH2 YPSKPDNPGDDAPAEDMAKYYSALRHYINLITRQRY-NH2 YPTKPENPGNDASPEEMTKYLIALRHYINLVTRQRY-NH2 TPTKPENPGNDASPQEMAKYMTALRHYVNLITRQRY-NH2 APSEPMHPGDQASPEQLAKYYDDWWQYITFITRPRF-NH2 APSEPMHPGDQASPEQLAKYYEDWWQYITFITRPRF-NH2 YPPKPESPGEDASPEEMNKYLTALTALRHYINLVTRQRY-NH2 APSEPQHPGGQATPEQLAQYYSDKYQYITFITRPRF-NH2 APSEPEHPGDNASPDELAKYYSDLWQYITFVGRPRY-NH2 GPTEPIHPGKDATPEELTKYYSDLYDYITLVGRSRW-NH TPSEPQHPGDQASPEQLAQYYSDLWQYITFVTRPRF-NH2 APSEPHHPGDQATPDQLAQYYSDLYQYITFITRPRF-NH2 APSEPHHPGDQATQDQLAQYYSDLYQYVTFITRPRF-NH2 YPSKPDNPGEDAPAEDMAKYYSALRHYINLITRQRY-NH2 YPSKPDNPGEDAPAEDMAKYYSALRHYINLITRQRY-NH2 YPSKPDNPGEDAPAEDMAKYYSALRHYINLITRQRY-NH2 YPPKPENPGEDASPEEMTKYLTALRHYINLVTRQRY-NH2 RLCIPYIIPC RLCIPVIFC FLPPCAYKGTC FPLPCAYKGTYC FFLPPCAYKGTC FFLPPCAHKGTC SVSNIPESIGF AVSNIPESIGF SVANIPESIGF IPPQFMRF-NH2 EGDEDEFLRF-NH2 SLKPAANLPLRF-NH2 SLKPAANLPLRF-NH2 SIPNLPQRF-NH2 YLSGKTKVQSMANLPQRF-NH2 AQYTNHFVHSLDTLPLRF-NH2 SLKPAANLPLRF-NH2 pEPWLPFG-NH2 pEPWIPFV-NH2 pEPWLPFV-NH2 pETWLPFV-NH2 pEPWLPFR-NH2 pEQY(SO3)TGWMDF-NH2 GLLDILKKVGKVA-NH2 EGMIGTLTSKRIKQ KCVNLQANGIKMTQECAKEDTKCLTLRSLKKTLKFCASGRTCTTMKIMSLPGEQITCCEGNMCNA LKCVNLQANGIKMTQECAKEDNKCLTLRSLKKTLKFCASDRICKTMKIMSLPGEKITCCEGNMCNA LKCVNLQANGVKMTQECAKEDTKCLTLRSLKKTLKFCASDRICKTMKIASLPGEQITCCEGNMCNA AQDYRCQLSRNYGKGSGSFTNYYYDKATSSCKTFRYRGSGGNGNRFKTLECEATCVTAE ASDYRCNLSRSYGKGSGSFTNYYYDKATNSCKTFTYRGTGGNGNRFKTLEECETTC AAADHRCGLIRNLGKGSGSFTNYYYDKATNSCKTFTYRGTGGNGNRFKTLEECGTTCVTG

CSM, VC CSM CSM RRN RRN RRN RRN RRN RRN RRN RRN RRN RRN RRN RRN RRN RRN RRN RRN RRN RRN RRN RRN CSM LLA LLA NA NA NA CSM, SP RI RI NA NA TNS SGHR SGHR SGHR SGHR SGHR CSM CSM CSM CSM CSM CSM, IAE IN NA TAIC TAIC TAIC TAIC TAIC TAIC

RT229 BM231 LC230 ST246 ST246 ST246 XL236,238,255 XL236,238,255 XL236,238,255 XL236,238,255 XL236,238,255 XL236,238,255 PB256 RR241 SI241 TN241 BuM241 RCA,247 RS241 RT232 RR233 RT234 TN243 PB,232 RR255 CR, CS253,254 CR252 CR252 CR252 CR252 CR252 LRO86 LRO95 LRO95 KM215 PV215 RE214 RCA257 RCA257 RCA257 RCA257 RCA258 LPE142 LPE142 LPE142 LPE142 LPE142 LL141 LL141 XL250 XL248 XL248 XL248 HA, HS2,33 HA, HS2,33 HA, HS2,33

a

CSM, contracts smooth muscle; IAE, induces analgesic effect; IN, inhibits nNOs; LLA, immunoregulates lymphocyte activity; NA, activity not tested; RI, regulates immunity; SGHR, stimulates growth hormone release; SP, splenocyte proliferator; TNS, transmits nociceptive stimuli; VC, vasoconstriction; RRN, regulates pituitary, gastrointestinal tract, and numerous other functions; TAIC, acts on ion channels. bBM, Bombina maxima; BuM, Bufo marinus; CR, Crinia riparia; CS, Crinia signifera; HA, Hyla annectans; HS, Hyla simplex; KM, Kassina maculata; LC, Litoria caerulea; LL, Litoria lesueuri; LPE, Litoria peronii; LRO, Litoria rothii; PB, Phyllomedusa bicolor; PV, Phylictimantis verrucosus; RCA, Rana catesbeiana; RE, Rana esculenta; RR, Rana ridibunda; RS, Rana sylvatica; RT, Rana temporaria; SI, Siren intermedia; ST, Silurana tropicali; TN, Typhlonectes natans; XL, Xenopus laevis. O


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behavioral, neuroendocrine, and autonomic functions.214 RFamide peptides identified from the skin secretions of the hyperoliid frogs are IF-8 amide from K. maculata and EF-10 amide from Phylictimantis verrucosus. The C-terminal FMRFNH2 and FLRF-NH2 of both peptides are positive structural motifs for the FMRF amide-related peptides (FaRPs) family that exists ubiquitously in invertebrates and contains F/Y/ WM/L/I/V/F/TRF-NH2 at the C-terminus. In addition, from the terminal F-NH2 of FaRPs, position 3 is a hydrophobic and position 4 is an aromatic residue. Therefore, IF-8 amide and EF-10 amide are the first canonical FaRPs from vertebrate sources with endectocide function. The cDNA sequence encoding IF-8 amide has a single copy of the peptide located at the C-terminus of the open reading frame that encodes 58 aa.215 2.6.2. Bv8. Bv8 from amphibian skins is a member of Bv8prokineticin family. Its orthologs have been found from invertebrates to humans. For example, Bv8 from skin secretions of B. variegate and B. bombina are related to a nontoxic component of the venom of the black mamba, protein A.216−218 Current genetic analysis predicts that homologues of Bv8 exist in skin secretions of R. temporaria and R. esculenta. Biochemical purification demonstrated the existence of homologues of Bv8 in the skin secretion of B. orientalis (Bo8) and B. maxima (Bm8a). These proteins originate from simple precursors containing a putative 19-residue signal that is 100% identical in all three proproteins and the mature protein, which share high similarity. For example, the sequences of Bo8 and Bm8a are 96% and 92% identical to Bv8. Comparison of the aa sequence of Bv8 in amphibian, rat, human, and snake shows that all contain AVITG at N-terminus and 10 C with identical spacers. The hydrophobic AVITG sequence of frog Bv8 forms a “beak” that is exposed at the surface of the tightly folded protein in a structural model. The bioactivities of Bv8 in amphibians have been tested on isolated organs, such as guinea pig, rat, and mouse ileum and rabbit jejunum. AVITGA is crucial for bioactivity because deletions and substitutions of this motif yield inactive and sometimes antagonist molecules. At 5−10 ng/mL, Bv8 stimulates the longitudinal contraction of the guinea pig ileum smooth muscle. At 2.5−25 nM, Bv8 also contracts mouse and rat ileum and increases the smooth muscle tone of the rabbit jejunum and guinea pig colon in a doseindependent manner.217,219 EDTA treatment, antagonists, and the Ca2+-channel blocker nifedipine do not affect the contraction of guinea pig ileum stimulated by Bv8. Injection of Bv8 into the brains of rats induces hyperalgesia in a dosedependent manner that is always accompanied by an increase in blood pressure and behavioral changes.217 In addition, Bv8 and its mammalian orthologs modulate complex behaviors and physiological process such as circadian rhythms, pain perception, drinking, feeding, hypothalamic hormone release, neuronal survival, and angiogenesis.217,220−223 2.6.3. Neuromedin U. The neuromedin U (NmU) peptides sharing limited sequence homology to members of other peptide families and are important in the gut/genitourinary system. NmU peptides stimulate uterine smooth muscle contraction, regulate ion transport and mesenteric blood flow in the intestine, and affect some hormone generation and secretion.224−226 In addition, their presence in various brain regions shows they also have central functions.227,228 Several NmU analogs have been discovered in the skins of B. maxima, L. caerulea, and R. temporaria.229−231 The aa sequence of NmU23 from L. caerulea, which can contract rat uterine, is highly

identical to peptides from R. temporaria and other vertebrate.230 The C-terminal FFLFRPRN residues of Bm-NmU-17 from B. maxima, which contract the smooth muscle of rat uterus horns in a concentration-dependent manner, are the same as residues of NmU from mammals and other frog species. Nevertheless, the N-terminal DSSGIVGRP sequence is different from NmU peptides from different sources. Research on the nucleotide sequence of Bm-NmU-17 shows that the encoded 145 aa precursor contains a single repeat of a peptide at the Cterminus that is preceded by KR and followed by GRK as sites for cleavage and release of the mature peptide.231 2.6.4. Neuropeptide Y Family. Pancreatic polypeptide (PP), neuropeptide tyrosine (NPY), and peptide tyrosinetyrosine (PYY) belong to the neuropeptide Y family and were first found to be expressed in the mammalian brain, pancreas, and gut. All neuropeptide Y peptides possess 36 aa, contain a C-terminal Y or F amide, and share common tertiary structural features. Neuropeptide Y and the related peptides PYY and PP are involved in feeding behavior, regulation of the pituitary and the gastrointestinal tract, and numerous other functions. PYY peptide was first isolated from P. bicolor in the 1990s.232 Subsequently, all three members of the neuropeptide Y family have been discovered in a variety of frog species such as NPY from R. ridibunda and PP from R. catesbeiana.233−247 2.6.5. Xenoxins. Xenoxin-1, -2, and -3 from the skin ssecretion of X. laevis have 66 aa containing 8 C without H, Y, and W.248 The structural organization of these peptides shares high similarity with neurotoxin/cytotoxin peptides found previously in snake venom. Xenoxins interact with membrane receptors or ion channels and with the phospholipid bilayer.248 Xenoxins, especially xenoxin-1, directly activate dihydropyridine-sensitive Ca2+ channels in the mammalian epithelium.249 Xenoxin-1 added to villus epithelial cells with Na+ activates volume reduction. Volume changes caused by xenoxin-1 are dependent on Ca2+ influx.249 The function of xenoxin-1 is similar to that of bay K-8644, a selective agonist of dihydropyridine-sensitive Ca2+ channels. However, xenoxin-1 and xenoxin-2 have no neurotoxin, antiprotease, or antimicrobial activities. 2.6.6. Neurotoxins. Annoxin, a 60 aa peptide from the skin secretions of the tree frog H. annectans, is the first geneencoded neurotoxin discovered in amphibians. It has a similarity of 44% and 53% to dendrotoxin δ-DaTX and protease inhibitor K identified from green mamba venoms, respectively. Annoxin contains conserved interactive sites (KGSGST) that inhibit trypsin. Anntoxin inhibits neuronal terodotoxin-sensitive voltage-gated sodium channels in adult rat dorsal root ganglion neurons with an IC50 3.4 μM. Additionally, a low dose of anntoxin is toxic to several potential predators including birds, insects, snakes, and mice and can induce death, showing that anntoxin possibly helps H. annectans defend against predators.2 The structural organization of the anntoxinS1 and anntoxin-S2 from the skin secretions of another tree frog, H. simplex, shares high similarity with annoxin. Similar to annoxin, anntoxin-S1 and anntoxin-S2 inhibit terodotoxinsensitive voltage-gated sodium channels in a dose-dependent manner.33 2.6.7. Levitide. Levitide from X. laevis skin secretions has neurohormone activity and has a high similar structural organization to xenopsin. The preprolevitide sequence at both the nucleotide and aa levels is highly homologous to preproxenopsin. The single KR cleavage site in prolevitide is important for the proteolytic release of many hormones from P


Chemical Reviews

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Table 8. Antioxidant Peptides from Amphibians

a

name

sequence

other functiona

species/ref

antioxidin-RL pleurain-A1 pleurain-D1 pleurain-E1 pleurain-G1 pleurain-J1 pleurain-K1 pleurain-M1 pleurain-N1 pleurain-P1 pleurain-R1 antioxidin-RP1 antioxidin-RP2 APBSP APBMH japonicin-1Npa japonicin-1Npb parkerin macrotympanain-A1 margaratain-A1 margaratain-B1 margaratain-C1 odorranian-A-OA11 odorranian-A-OA12 andersonin-H3 andersonin-R1 andersonin-C1 andersonin-N1 andersonin-G1 antioxidin-RL lividin-D1 schmackerin-C1 tiannanin-A1 wuchuanin-E1 wuchuanin-C1 wuchuanin-D1 wuchuanin-A1 hejiangin-A1 hejiangin-E1 hejiangin-F1

AMRLTYNRPCIYAT SIITMTKEAKLPQLWKQIACRLYNTC FLSGILKLAFKIPSVLCAVLKNC AKAWGIPPHVIPQIVPVRIRPLCGNV GFWDSVKEGLKNAAVTILNKIKCKISECPPA FIPGLRRLFATVVPTVVCAINKLPPG DDPDKGMLKWKNDFFQEF GLLDSVKEGLKKVAGQLLDTLKCKISGCTPA GFFDRIKALTKNVTLELLNTITCKLPVTPP SFGAKNAVKNGLQKLRNQCQANNYQGPFCDIFKKNP CVHWMTNTARTACIAP AMRLTYNKPCLYGT SMRLTYNKPCLYGT LEELEEELEGCE LEQQVDDLEGSLEQEKK FLLFPLMCKIQGKC FVLPLVMCKILRKC GWANTLKNVAGGLCKITGAA FLPGLECVW VTPPWARIYYGCAKA FFSTSCRSGC GMLKWKNDFFHFLQWLLISCQNYFVK VVKCSYRQGSPDSR VVKFSYRKGSPAPQKN VAIYGRDDRSDVCRQVQHNWLVCDTY ENAEEDEVLMENLFCSYIVGSADSFWT TSRCIFYRRKKCS ENMFNIKSSVESDSFWG KEKLKLKAKAPKCYNDKLACT AMRLTYNRPCIYAT KNNFCQVLYVWLLRLGKQCFVKFSKDVET AAPRGGKGFFCKLFKDC LLPPWLRPRNG CVDIGFSPTGKRPPFCPYPG VFLGNIVSMGKKI DAAVEPELYHWGKVWLPN APDRPRKFCGILG RFIYMKGFGKPRFGKR SADQTGMNKAALSPIRFISKSV IPWKLPATFRPVERPFSKPFCRKD

no AM AM AM, AI AM, AI AM, AI AI AM, AI AI AM, AI AM AI AI no no HR, AM HR, AM HR, AM IM IM IM no IM IM IM IM AM, IS IM, IS IM, IS no IM IM IM, IS IM, IS IM, IS IS no AM no no

O. livida273 R. pleuraden272 R. pleuraden272 R. pleuraden272 R. pleuraden272 R. pleuraden272 R. pleuraden272 R. pleuraden272 R. pleuraden272 R. pleuraden272 R. pleuraden272 R. pleuraden272 R. pleuraden272 R. catesbeiana271 R. catesbeiana270 N. parkeri274 N. parkeri274 N. parkeri274 O. macrotympana196 O. margaratae96 O. margaratae96 O. margaratae96 O. margaratae96 O. margaratae96 O. margaratae96 O. margaratae96 O. margaratae96 O. margaratae96 O. andersonii96 O. livida273 O. livida275 O. schmackeri275 O. tiannanensis275 O. wuchuanensis275 O. wuchuanensis275 O. wuchuanensis275 O. wuchuanensis275 O. hejiangensis275 O. hejiangensis275 O. hejiangensis275

AM, antimicrobial; AI, anti-inflammatory; HR, histamine release; IM, immunomodulation; IS, insulin-stimulating activity; no, no other function.

their prohormones. Levitide is found in the skin exudate of X. laevis at concentrations similar to those of the mammalian-like neuropeptides cerulein and xenopsin. Furthermore, a pyroglutamic acid residue has been found at the N-terminus and amidated C-terminus of levitide. These results suggest that levitide may be a neuropeptide or a neuropeptide analog.250 2.6.8. Rothein 1. Rothein 1 peptides co-occur with caeruleins 1.1 and 1.2 in the secretions from L. rothii dorsal glands and have lymphocyte proliferator activity and induce smooth muscle contraction.86,95 Rothein 1-related peptides rothein 2, 3, and 4.1 from L. rothii show no activity.86 Rotheins 1.1 and 1.2, whose S1 and S3 are sequentially replaced by the A residue, enhance lymphocyte proliferation by about 50% as compared to the original peptides. Replacements of the Cterminal F or any other hydrophilic residue with A lead to loss of all bioactivities,95 suggesting that both hydrophilic and hydrophobic interactions between rothein 1 and CCK2 transmembrane receptors are important. However, a combina-

tion of (31)P and (2)H solid-state nuclear magnetic resonance studies shows that rothein 1 does not interact with a model membrane at 25 °C. In contrast, signiferin 1 and riparin 1.1 with a cyclic disulfide interact with phospholipid head groups and partially penetrate the upper leaflet of a model membrane to different degrees.251 Thus, other hypotheses are necessary to explain the bioactivities of rothein 1 peptides. 2.6.9. Small Neuropeptides Containing One Disulfide Bridge. A family of small neuropeptides containing a single disulfide bridge from the skin glands of Crinia frogs includes signiferin 1 from C. signifera and C. deserticola, and riparin 1.1 and riparin 1.2 from C. riparia.252−254 These short peptides contain 9−11 aa and a single intramolecular disulfide bridge and have either smooth muscle activity or immunomodulation, acting through G-protein coupled CCK2 receptors.252 Despite the similarity in the sequences of signiferin 1 and riparin, they have different bioactivities. Signiferin 1 contracts guinea pig ileum at nanomolar concentrations and affects proliferation of Q


Chemical Reviews

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Table 9. Insulin-Releasing Peptides from Amphibians name caerulein-B1 caerulein-B2 xenopsin xenopsin-AM2 brevinin-2GUb FSIP ITP 2 pseudin-2 phylloseptin-L2 pipinin-1 KC-19 BV8 ranatuerin-2CBd brevinin-1CBb ranatuerin-1CBb ranatuerin-2CBc temporin-CBf palustrin-2CBa temporin-CBa ranatuerin-1CBa brevinin-1E brevinin-2EC esculentin-1 esculentin-1B palustrin-1c brevinin-1 GM-14 IN-21 peak 21 peak 22 peak 23 CPF-1 CPF-3 CPF-4 CPF-5 CPF-6 CPF-7 magainin II magainin I PGLa XPF-1 CPF-SE1 CPF-SE2 CPF-SE3 RK-13 dermaseptin-B tigerinin-1R magainin-AM1 magainin-AM2 CPF-AM1 PGLa-AM1 temporin-1Vb temporin-1Oe temporin-1DRb temporin-1TGb temporin-1Va temporin-1Vc gaegurin-6 B2RP kassinatuerin-1 ascaphin-1

speciesa/ref

sequence pEQDY (SO3) GTGWMDF-NH2 pEDY (SO3) TGWMDF- NH2 EGKRPWIL pEGRRPWIL GVIIDTLKGAAKTVAAELLRKAHCKLTNSC AVWKDFLKNIGKAAGKAVLNSVTDMVNE MLADVFEKIMGD... GLNALKKVFQGIHEAIKLINNHVQ FLSLIPHVISALSSL-NH2 FLPIIAGVAAKVFPKIFCAISKKC KGAAKGLLEVASCKLSKSC AVITGACERDVQCGGGTCCAVSLI... GFLDIIKNLGKTFAGHMLDKIRCTIGTCPPSP FLPFIARLAAKVFPSIICSVTKKC SMFSVLKNLGKVGLGFVACKVNKQC GFLDIIKNLGKTFAGHMLDKIKCTIGTCPPSP FLPIASMLGKYL-NH2 GFLDIIKDTGKEFAVKILNNLKCKLAGGCPP FLPIASLLGKYL-NH2 SMLSVLKNLGKVGLGFVACKINKQC FLPLLAGLAANFLPKIFCKITRKC GILLDKLKNFAKTAGKGVLQSLLNTASCK LSGQC GIFSKFGRKKIKNLLISGLKNVGKEVGMDVVRTGIDIAGCKIKGEC GIFSKLAGKKLKNLLISGLKNVGKEVGMDVVRTGIDIAGCKIKGEC ALSILRGLEKLAKMGIALTNCKATKKC FLPVLAGIAAKVVPALFCKITKKC GKPFYPPPIYPEDM IYNAICPCKHCNKCKPGLLAN Pyr-QRLGHQWAVGHLM Pyr-DSFGNQWARGHFM Pyr- QRLGNQWAVGHLM GLASFLGKALKAGLKIGAHLLGGAPQQ GFGSFLGKALKAALKIGANALGGSPQQ GLASLLGKALKAGLKIGTHFLGGAPQQ GFGSFLGKALKTALKIGANALGGSPQQ GFASFLGKALKAALKIGANMLGGAPQQ GFGSFLGKALKAALKIGANALGGAPQQ GIGKFLHSAKKFGKAFVGEIMNS GIGKFLHSAGKFGKAFVGEIMKS GMASKAGAIAGKIAKVALKAL-NH2 GWASKIGQTLGKIAKVGLQGLMQPK GFLGPLLKLGLKGVAKVIPHLIPSRQQ GFLGPLLKLGLKGAAKLLPQLLPSRQQ GFLGSLLKTGLKVGSNLL-NH2 RRKPLFPFIPRPK ALWKDILKNVGKAAGKAVLNTVTDMVNQ RVCSAIPLPICH-NH2 GIKEFAHSLGKFGKAFVGGILNQ GVSKILHSAGKFGKAFLGEIMKS GLGSVLGKALKIGANLL-NH2 GMASKAGSVLGKVAKVALKAAL-NH2 FLSIIAKVLGSLF-NH2 ILPLLGNLLNGLL-NH2 NFLGTLVNLAKKIL-NH2 AVDLAKIANKVLSSLF-NH2 FLSSIGKILGNLL-NH2 FLPLVTMLLGKLF-NH2 FLPLLAGLAANFLPTIICKISYKC GIWDTIKSMGKVFAGKILQNL-NH2 GFMKYIGPLIPHAVKAISDLI-NH2 GFRDVLKGAAKAFVKTVAGHIAN-NH2 R

96

XB, LCA XB96 XA, XL96 XA96 HG280 AL289 AL289 PP291 HL280 LP293 RS293 RS293 LC282 LC282 LC282 LC282 LC282 LC282 LC282 LC282 RS285 RS285 RS285 RS285 RP283 RB283 BV54 BV54 BV54 BV54 BV54 XL108 XL108 XL108 XL108 XL108 XL108 XL108 XL108 XL108 XL108 SE108 SE108 SE108 AC290 PT288 HR286 XA109 XA109 XA109 XA109 LV281 RO281 RD281 RT281 LV281 LV281 RR287 LS278 KS292 AT292

other activityb no no no no CL, AM no no AM AM AM, HR AM UK no CT no AM no no no AM AM AM AM AM AM AM, CL AM, CL AM, CL UK UK UK AM AM AM AM AM AM AM AM AM AM AM AM AM no AM no no no no no AM AM AM AM AM, CT AM, CT AM AM AM AM, CL

threshold concn (nM) 30 30 30 30 100 UKd UK 10 30 UK UK UK 30 100 300 1000 300 300 300 300 UK UK UK UK UK UK UK UK UK UK UK 0.03 0.03 0.1 0.03 0.03 3 100 30 100 0.1 0.03 0.03 0.03 10 UK 0.1 10 1 30 30 10 1000 1000 10 100 100 UK 1000 10 100

MRc (%) UKd UK UK UK 373 UK UK UK 301 UK UK UK 236 285 UK UK UK UK UK UK UK UK UK UK UK UK UK UK UK UK UK 285 296 348 223 444 537 290 342 468 307 564 465 365 UK UK 405 UK UK UK UK UK UK UK UK UK UK UK 222 UK UK


Chemical Reviews

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Table 9. continued name ascaphin-8 ranatuerin-1 peptide XT-7 fallaxin MLP andersonin-C1 andersonin-D1 andersonin-G1 andersonin-N1 andersonin-Q1 hejiangin-A1 tiannanin-A1 wuchuanin-C1 wuchuanin-E1

speciesa/ref

sequence

292

AT RCA292 XT292 LF292 RT292 OA275 OA275 OA275 OA275 OA275 OH275 OT275 OW275 OW275

GFKDLLKGAAKALVKTVLF-NH2 SMLSVLKNLGKVGLGFVACKINKQC GLLGPLLKIAAKVGSNLL-NH2 GVVDILKGAAKDIAGHLASKVMNKL-NH2 AIGSILGALAKGLPTLISWIKNR-NH2 TSRCIFYRRKKCS FIFPKKNIINSLFGR KEKLKLKAKAPKCYNDKLACT ENMFNIKSSVESDSFWG QMFHLWYLRHMKNKKPMA RFIYMKGFGKPRFGKR LLPPWLRPRNG VFLGNIVSMGKKI CVDIGFSPTGKRPPFCPYPG

other activityb

threshold concn (nM)

MRc (%)

AM, CL AM AM AM, CL AM, CL AM, ATO AM, IM IM, ATO IM IM AM ATO IM, ATO ATO

10 1000 1000 100 1000 50 μg/mL 50 μg/mL 50 μg/mL 50 μg/mL 50 μg/mL 50 μg/mL 50 μg/mL 50 μg/mL 50 μg/mL

UK UK UK UK UK UK UK UK UK UK UK UK UK UK

a

AC, Agalychnis calcarifer; AL, Agalychnis litodryas; AT, Ascaphus truei; BV, Bombina variegate; HG, Hylarana guentheri; HL, Hylomantis lemur; HR, Hoplobatrachus rugulosus; KS, Kassina senegalensis; LC, Litoria citropa; LCA, Lithobates catesbeianus; LF, Litoria fallax; LP, Lithobates pipiens; LS, Lithobates septentrionalis; LV, Lithobates virgatipes; OA, Odorrana andersonii; OH, Odorrana hejiangensis; OT, Odorrana tiannanensis; OW, Odorrana wuchuanensis; PP, Pseudis paradoxa; PT, Phyllomedusa trinitatis; RB, Rana brevipoda porsa; RCA, Rana catesbeiana; RD, Rana draytonii; RO, Rana ornativentris; RP, Rana palustris; RR, Rana rugosa; RS, Rana saharica; RT, Rana tagoi; SE, Silurana epitropicalis; XA, Xenopus amieti; XB, Xenopus borealis; XL, Xenopus laevis; XT, Xenopus tropicalis. bAM, antimicrobial; ATO, antioxidant; CL, cytolytic; CT, cytotoxic; HR, histamine-releasing; IM, immunomodulating. cMR: maximum increase in the rate of insulin release at 3 μM. dUK: unknown.

lymphocytes at 10−6 M.252,253 Riparin 1.1 and riparin 1.2 show lymphocyte activity but do not contract smooth muscle. Thus, these peptides on amphibian skins appear to have functions other than smooth muscle activity.252

few seconds in a dose-dependent manner, indicating high radical-scavenging efficiency. For example, antioxidin-RP1 at 20 μg/mL scavenges 50% of DPPH within 2 min, while antioxidinRP1 at 80 μg/mL scavenges 85% of DPPH within 5 s and nearly 100% within 4 min.272 Site-specific mutagenesis experiments show that some key residues such as M, free C, P, Y, and W, and intramolecular disulfides have varying effects on antioxidant function. For example, Y6, Y12 replacement with G and C10 alkylation in antioxidin-RP1 and antioxidin-RL strongly decrease antioxidant ability.273

2.7. Antioxidant Peptides

Because of the special habitats and environments of amphibians, they sometimes have nonbiological injuries from reactive oxygen species.259,260 These active radicals can peroxidate lipids, denature proteins, and damage nucleic acids, leading to severe consequences to overall metabolism and enormous damage to cell and tissues.261 To antagonize enhanced oxidative stress, amphibian skin has evolved an efficient antioxidant defense system with two major groups. The first group is antioxidant enzymes such as peroxidase, catalase, glutathione, and superoxide dismutase.262−268 The second group comprises low-molecular-weight antioxidants such as glutathione, nicotinamide adenine dinucleotide, carnosine, carotene, polyphenols, uric acid, and lipoic acid that clear reactive oxygen species by donating electrons.264−269 Studies of the amphibian skin antioxidant system have reported many antioxidant peptides from amphibian skin secretions identified by purification, proteomic analysis, or cDNA trapping (Table 8). Two peptides from R. catesbeiana muscle and skin proteins hydrolyzed with different enzymes are effective free radial scavengers in lipid peroxidation inhibition tests and direct free radical scavenging assays.270,271 The first report of a gene-encoded antioxidant peptide was the 11 different families of antioxidant peptides characterized from R. pleuraden skin including pleurains A, D, E, G, J, K, M, N, P, and R and antioxidin-RP.272 All of these antioxidant peptides have 14−36 aa and a molecular mass of 1−4 kDa. Among the 11 families, 7 exert both strong antioxidant activities on free radical scavenging tests (ABTS+, DPPH, NO scavenging) and antimicrobial activities (pleurains A, D, E, G, J, M, R). The other four families have only antioxidant activities.272 Other antioxidant peptides identified from skin secretions of O. livida by peptide fractionation scavenge free radicals within a

2.8. Lectins

Sugar-binding lectins that are highly specific for the sugar moieties on glycoprotein or glycolipid of cell surface have been extensively studied for more than 20 years and have potential for drug delivery and targeting.276,277 Odorranalectin, the smallest peptide containing lectin-like activity, was purified from the skin secretions of O. grahami and has a sequence of YASPKCFRYPNGVLACT.3 Two C residues of this peptide form an intramolecular disulfide bond. The overall structure of the odorranalectin precursor deduced from its cDNA shows significant similarity to amphibian AMPs, implying they might have the same ancestors. With carbohydrate-binding specificity, odorranalectin at 0.75 μg/mL strongly agglutinates untreated rabbit, human erythrocytes, and microorganisms. The hemagglutination-inhibition test demonstrates that L-fucose specifically inhibits hemeagglutination induced by odorranalectin. In addition, odorranalectin is stable in plasma for more than 5 h, suggesting good bioavailability, and can be specifically conjugated to spleen, liver, and lung after intravenous injection. Toxicity and immunogenicity of odorranalectin are extremely low. Thus, odorranalectin is an excellent candidate for drug delivery and targeting.3 2.9. Insulin-Releasing Peptides

Many frog skin peptides first identified as AMPs have subsequently displayed insulin-releasing activity in a rat clonal BRIN-BD11β-cell assay system.278−280 To date, insulinS


Chemical Reviews

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Table 10. Mast Cell-Degrading and Histamine-Releasing Peptides from Amphibians name

sequence

MCDa

AMb

other functionc

species/refd

XO-4 granuliberin-R temporin-Ma esculentin-2SE esculentin-1SEa esculentin-1SEb brevinin-1SE ranatuerin-2SEa ranatuerin-2SEb ranatuerin-2SEc esculentin-2SE kassinakinin S kassorin S pipinin-1 pLR pYR kassorin M OdE1 OdK1 OdH1 OdA1 OdL1 OdM1 OdP2a OdQ1 OdU1 nigrocin-OG2 nigrocin-OG4 nigrocin-OG21 OdI1 OdJ1 OdF1 OdG1 OdB1 OdC1 OdD1 OdN1 OdO1 OdP1a OdR1 OdS1 OdW1 nigrocin-OG5 nigrocin-OG13 nigrocin-OG20 nigroain-C2 nigroain-E1 nigroain-K1 rugosin-RN1 rugosin-RN3 rugosin-RN5 nigroain-B1 nigroain-K2 gaegurin-RN1 gaegurin-RN4 gaegurin-RN5 temporin-RN1 temporin-RN3 brevinins-ALb japonicin-1Npa japonicin-1Npb

FIKQLLPHLPGWIDAVSNAFS-NH2 SNTALRRYNQWATGHFM FLPIVGKLLSGLSGLL GFFSLIKGVAKIATKGLAKNLGKMGLDLVGCKISKEC GLFSKFNKKKIKSGLIKIIKTAGKEAGLEALRTGIDVIGCKIKGEC GLFSKFNKKKIKSGLFKIIKTAGKEAGLEALRTGIDVIGCKIKGEC FLPLVRGAAKLIPSVVCAISKRC GFISTVKNLATNVAGTVIDTIKCKV AIMDTIKDTAKTVAVGLLNKLKCKITGC GIMDTIKDTAKTVAVGLLNKLKCKITGC GFFSLIKGVAKIATKGLAKNLGKMGLDLVGCKISKEC FIPVTLLALHKIKEKLN-NH2 FLGGILNTITGLL-NH2 FLPIIAGVAAKVFPKIFCAISKKC LVRGCWTKSYPPKPCFVR YLKGCWTKSYPPKPCFSR FLEGLLNTVTGLL-NH2 GLGGAKKNFIIAANKTAPQSVKKTFSCKLYNG GLFTLIKGAAKLIGKTVPKKQARLGMNLWLVKLPTNVKT GIFGKILGVGKKVLCGLSGVC VVKCSYRLGSPDSRCN VEVQVRDKGKGIYGLSPLRQPAP ATAWDFGPHGLLPIRPIRIRPLCGKDKS GLLSGILGAGKHIVCGLSGPCQSLNRKSSDVEYHLAKC APFCLGYLSPKLKDMEPKPRG GCSRWIIGIHGQICRD GLLGKILGVEKRVLCGLSGMC GLLGKILGAGKHIICGLSGLC GLLGKILGAGKIKVDGLSGLC GFFTLIKAANKLINKTVNKEAGKGGLEIMA GLFTLIKCAYQLIAPTVACN GFMDTAKNVAKNVAVTLLDNLKCKTTKAC FMPILSCSRFKRC AALKGCWTKSIPPKPCFGKR GVLGAVKDLLIGAGKSAAQSVLKTLSCKLSNDC GFLDTFKNLALNAAKSAGVSVLNSLSCKLFKTC DEKGPKWKR AVPLIYNRPGIYVTKRPKGK VIPFVASVAAEMMQHVYCAASKKC GFSPNLPGKGLRIS FLPPSPWKETFRTS GLFGKSSVWGRKYYVDLAGCAKA GLLGKILGAGKQKVCGLSGLC GLLGKILGAGKHIVCGLSGLR GLLGKILGAGKHIVCGLSGLC FKTWKRPPFQTSCWGIIKE DCTRWIIGINGRICRD SLWETIKNAGKGFIQNILDKIR SIRDKIKTIAIDLAKSAGTGVLKTLICKLDKSC SIRDKIKTIAIDLAKSAGMGILKTLICKLDKSC SIRDKIKTIAIDLAKSAGTGVLKTLICKLNKSC CVISAGWNHKIRCKLTGNC SLWETIKNAGKGFILNILDKIRCKVAGGCKT FIGPVLKIAAGILPTAICKIFKKC FVGPVLKIAAGILPTAICKIYKKC FLGPIIKIATGILPTAICKFLKKC FLPLVLGALSGILPKIL-NH2 FFPLLFGALSSHLPKLF-NH2 FLPLAVSLAANFLPKLFCKITKKC FLLFPLMCKIQGKC FVLPLVMCKILRKC

UK + + + + + + + + + + + + UK UK UK + + + + + + + + + + + + + + + + − + + + + + + − + + + + + + + + + + + + + + + + + + + +

+ + + + + + + + + + + UK + + UK UK − + + + − + + + − + − + + − + + + + + + + + + − + + + + + + + + + + + + + + + + + + + + +

no no no no no no no no no no no no no IR ID ID CSM IN no IN no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no AC AO AO

KM305 RRU306 AL307 RS300 RS300 RS300 RS300 RS300 RS300 RS300 RS300 KS299 KS308 LP284 RR206 RR201 KM308 OG309 OG309 OG309 OG309 OG309 OG309 OG309 OG309 OG309 OG309 OG309 OG309 OG309 OG309 OG309 OG309 OG309 OG309 OG309 OG309 OG309 OG309 OG309 OG309 OG309 OG309 OG309 OG309 RN4 RN4 RN4 RN4 RN4 RN4 RN4 RN4 RN4 RN4 RN4 RN4 RN4 AL307 NP274 NP274

T


Chemical Reviews

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Table 10. continued name parkerin catesbeianalectin

MCDa

sequence GWANTLKNVAGGLCKITGAA RQRDVDQEERRDDPGERNVQVEKRFLTFPGMTFGKLLGK

+ +

AMb + +

other functionc no no

species/refd NP274 RCA310

a

MCD, mast cell degranulation; UK, unknown. bAM: antimicrobial. cIR, insulin-releasing agent; ID, inhibits early development of granulocyte macrophage colonies from bone marrow stem cells; CSM, contracts smooth muscle of guinea pig urinary bladder; IN, inhibits NO release; AC, anticancer; AO, antioxidant. dAL, Amolops loloensis; KM, Kassina maculate; KS, Kassina senegalensis; LP, Lithobates pipiens; NP, Nanorana parkeri; OG, Odorrana grahami; RCA, Rana catesbeiana; RN, Rana nigrovittata; RRU, Rana rugosa; RS, Rana sevosa.

with release of lactate dehydrogenase, such as temporin-1Va and -1Vc, ascaphin-1, fallaxin, and melittin-related peptide, the insulin-releasing effect is probably related to permeabilization of the plasma membrane, which might be a nonselectively toxic effect. For peptides producing a significant increase in insulin release without distinct release of lactate dehydrogenase, the mechanism of action could involve internalization, in which peptides facilitate release of insulin contained in secretory granules across the plasma membrane. Insulin secretion is regulated by the KATP channel-dependent and KATP channelindependent augmentation pathways. In the KATP channeldependent pathway, insulin secretion is triggered by an increase of the ATP to ADP ratio, opening of voltage-dependent Ca2+ channels, and closure of ATP-sensitive K+ channels. This leads to an increase in cytoplasmic intracellular Ca2+ and insulin exocytosis. This mechanism is especially true for CPF-1, CPF-3, CPF-4, CPF-5, CPF-6, CPF-SE2, CPF-SE3, tigerinin-1R, and brevinin-1 family peptides because removing extracellular Ca2+ and adding K+ channel activator as well as blocking L-type voltage-dependent Ca2+ channels abolishes their insulinreleasing activities, which are closely associated with membrane depolarization and an increase in intracellular Ca2+ concentration. Phylloseptin-L2, temporin-1Vb, -1Oe, -1DRb, and -1TGb, pseudin-2, brevinin-2Gub, RK-13, esculentin-1, esculentin-1B, bombesins, GM-14, and IN-21 all stimulate insulin release but preserve the integrity of the plasma membrane. This stimulatory action can be maintained in the absence of extracellular Ca2+ or the presence of verapamil and diazoxidem. Thus, the insulin-releasing mechanism does not primarily involve influx of Ca2+ or closure of ATP-sensitive K+ channels, at least as the primary mechanism. However, some differences have been noted among the insulin-releasing peptides. Synthetic RK-13 induces insulin release in a glucose-sensitive and dose-dependent manner through a cAMP-protein kinase A pathway that is independent of pertussis toxin-sensitive G proteins.290 Similarly, bombesins, GM-14, and IN-21 identified from the Bombinatonidae family stimulate insulin release through regulation pathways independent of G proteins.54 In contrast, the insulinotropic actions of esculentin-1 and esculentin-1B involve both cAMP-protein kinase A and C dependent on pertussis toxin-sensitive G-protein pathways.285

releasing peptides have been identified from 28 frog species in the families Ranidae, Hylidae, Pipidae, Bombinatonidae, Hyperoliidae, Ascaphidae, and Leptodactylidae (Table 9).54,96,108,279−292 For example, synthetic analogs of pseudin2, peptide XT-7, kassinatuerin-1, ascaphin-8, and ranatuerin-1 stimulate insulin release at concentrations that are not cytotoxic to cells. In addition, brevinin-2-related peptide (B2RP) from L. septentrionalis, phylloseptin-L2 from H. lemur, brevinin-2Gub from H. guntheri, and tigerinin-1R from H. rugulosus significantly improve glucose tolerance and enhance total insulin release in vivo.278−280,286 Among these peptides, the structurally similar X. laevis peptides CPF-1, CPF-3, CPF-5, and CPF-6 and the ortholog CPF-SE1 from S. epitropicalis show high potency at 3 × 10−11 M that markedly increases the rate of insulin release. CPF-SE2 and CPF-SE3 significantly increase the rate of insulin release of BRIN-BD11 cells at concentrations as low as 3 × 10−10 M. The lowest concentration producing an effect is 1 × 10−9 M for magainin-AM2; 3 × 10−8 M for phylloseptin-L2 and caerulein-B1; and 1 × 10−8 M for pseudin2, kassinatuerin-1, RK-13, CPF-AM1, temporin-1Vb, temporin1TGb, magainin-AM1, and ascaphin-8.96,291 Magainin I, PGLaAM1, and ranatuerin-2CBd, which are more effective than the well-characterized insulin-releasing GIP, GLP-1, and the antidiabetic tolbutamide under the same experimental conditions, are the most promising candidates for development into an agent for treating type 2 diabetes.109,286 Although most frog skin peptides have insulin-releasing activity at concentrations that are not cytotoxic to cells, many amphibian skin peptides such as brevinin-1, pipinin-1, rugosin A-like insulinotropic peptide, esculentins-1 and -1B, brevinins-1E and -2EC, and temporins possess significant insulin-releasing activity and strong cytolytic activity.281,283−285,293 Thus, the therapeutic potential of these agents for type 2 diabetes is severely limited by their appreciable cytolytic activity against mammalian cells and their potent histamine-releasing activities.284,294 In addition, xenopsin at high concentrations increases plasma insulin levels and induces hyperglycemia in dogs through marked stimulation of cortisol and glucagon release.295,296 These results suggest that either xenopsin or xenopsin-AM2 is unlikely to be developed into antidiabetic agents.96 Most frog skin insulin-releasing peptides are cationic and possess considerable amphipathic character with an α-helix and amidated C-terminus. Nevertheless, structure−activity relationships of insulin-releasing peptides from frog skins are not completely understood. According to a series of structure− activity studies of brevinin-2Gub, B2RP, pseudin-2, members of the temporin family, and their analogs, a possible relationship exists between hydrophobicity and insulin-releasing activity, with increasing cationicity reducing or abolishing activity.281 The mechanism of frog skin insulin-releasing peptides is also not completely understood. However, for peptides with relatively moderate potentiation of insulin-release concomitant

2.10. Mast Cells Degradation/Histamine-Releasing Peptides

Mast cells are an important component of the innate immune system. Histamine release by mast cells causes local capillary dilation and plasma extravasation that can enhance entry of skin secretion components into tissues. Mast cell degradation and histamine release is an important defense strategy of amphibians, although it is poorly researched. Peptides with mast cells degradation/histamine-releasing activities have been found from skin secretions of H. maculatus, L. pipiens, R. rugosa, K. senegalensis, K. maculata, O. grahami, R. nigrovittata, R. sevosa, U


Chemical Reviews

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2.11. Wound-Healing Peptides

A. loloensis, and Nanorana parkeri (Table 10). These peptides have diverse structures and functions. Pipinin and XO-4 are classical cationic amphipathic peptides from frog skins. Most of them can induce mast cell degranulation and histamine release to some degree. In contrast, pLR has no α-helical regions and possesses a disulfide-bonded internal loop that is quite different in structure as compared to this group of peptides. In addition, pLR has the highest histamine-releasing activity of the mast-cell degrading peptides due to its highly cationic property and four positive charges at pH 7.0.206 Sharing 77.8% homology with pLR is pYR, which has the rigid polyproline motif PPKP and two C residues at positions 5 and 15. Both pLR and pYR have flexible N- and C-termini with rigid loop regions formed by a disulfide bridge between the two C residues.201 Kassinakinin S has restricted but marked identity with histamine-release peptide II (HR-II) from the venom of the Oriental hornet Vespa orientalis.297 The α-helical structure and highly cationic features of kassinakinin S contribute to its activity.298 Analysis of skin-derived cDNAs of kassinakinin S shows a putative signal peptide domain rich in hydrophobic residues that precedes a “pro-” domain rich in acidic aa residues and several KR repeats, which are typical for cleavage and release of a mature peptide. Generally, the aa sequence of both signal peptide and “pro-” domains are highly homologous within a given species, and some regions of these domains are also similar in all amphibians.299 For pLR, the very high potency might be related to the activation of intracellular signaling mechanisms because the histamine-releasing ability of pLR is independent of its helicity. However, intact esculentin-2SE and its C-terminal heptapeptide loop can induce mast cell degradation and histamine release, while the central amphipathic domain is nonbioactive. This result suggests that the activity of esculentin is due to the electrostatic interaction between the cationic loop and the highly negatively charged surface of the mast cells.300 This is the classical mast cell activation process used by most peptides with mast cell degradation and histamine-releasing activities. Therefore, many cationic AMPs can activate mast cells and release histamine and other mast cell mediators. Thus, a peptide probably possesses both antimicrobial and mast cell degranulation and histamine-releasing properties if it has intrinsic membrane-interactive or perturbing properties.294 Putative AMPs from species included in Table 10 have mast cell degradation/histamine-releasing activity associated with a receptor-independent mechanism.301,302 This phenomenon suggests a potential function for AMPs in inflammation and systemic anti-infection processes.303 These attributes of cationic amphipathic peptides from amphibian skin secretions resemble peptides from the venom of hymenopteran insects such as mellitin from Apis mellifera, mast-cell degranulating peptides from honeybees, mastoparans from the venom of Polistes wasps, and vespid chemotactic peptides from the venom of Vespa hornets.304 These are examples of convergent evolution and suggest that the structural similarities of the peptides reflect functional optimization to some degree. Most peptides causing mast cell gradation and histamine release have antimicrobial activity and some have other functions. Pipinin is an insulin-releasing agent; pLR and pYR inhibit early development of granulocyte macrophage colonies from bone marrow stem cells; kassorin M contracts the smooth muscle of guinea pig urinary bladder.

Wound healing involves a highly integrated series of overlapping and interrelating phases including alteration of capillary permeability and cellular migration; proliferation of fibroblasts, endothelial cells, and epithelial cells in the injured area; and a dynamic balance among cells, collagen, and capillary vessels.311,312 Therefore, in theory, all peptides with a positive effect on inflammation, proliferation, and remodeling belong to the wound-healing peptides. Several studies have used amphibian skins to heal wounds.313−315 However, only a few peptides from amphibians are reported to have wound-healing functions. They include Bv8, bombesin, and EGF-releasing and VEGF-releasing peptides. Bv8 from B. variegata can affect inflammation, proliferation, and remodeling because it: (1) promotes neuronal survival;221 (2) selectively boosts proliferation, survival, and migration and fenestration of capillary endothelial cells;222 (3) affects the reproductive cycle and mobilization of hematopoietic cell and regulates hematopoiesis;316,317 and (4) induces macrophages to migrate and acquire a proinflammatory phenotype through the PKR-1 receptor of macrophages.155 A peptide family with EGF-releasing and VEGF-releasing activities was identified from H. simplex. The family has 11 members named hylareleasin 1−11. Most have 16 residues except for hylareleasin 8, which has 18. These peptides contain GLLD/NP at the N-terminus, increase HUVEC cell growth in a dose-dependent manner, and induce EGF and VEGF secretion by increasing protein kinases phosphorylation.33 Bombesin is a small peptide of 16 aa first isolated from B. bombina. In an experimental model of mechanical injury to human keratinocytes, treatment with bombesin modulates expression of several important skin repair factors such as TGFβ, IL-8, COX-2, VEGF, and TLR2, and promotes migration, proliferation, and neoangiogenesis in the damaged tissue.318,319 Keratinocytes are important for maintaining skin integrity and are the first cells to respond to injury. Several neuropeptides in the peripheral nerves of skin such as vasoactive intestinal peptide (VIP), calcitonin gene-related peptide (CGRP), peptide histidine methionine, and growth hormonereleasing (GHR) factor stimulate cAMP formation and promote the growth of keratinocyte cell lines.320,321 In theory, neuropeptides that help the proliferation of keratinocyte cell lines also belong to the wound-healing peptides. The peptide pbCGRP from the skin exudates of the frog P. bicolor has the sequence SCDTSTCATQRLADFLSRSGGIGSPDFVPTDVSANSF-NH2, which includes a disulfide bridge between C2 and C7 and differs from human α-CGRP at position 16.322 As compared to the human counterparts of pbCGRP, which bind the CGRP-1 receptor, C-terminal fragments of pbCGRP have higher antagonistic potency and affinity. One fragment, pbCGRP (8−37), is the strongest competitive antagonist to CGRP-1 among all natural proteins reported to date.323 Pituitary adenylate cyclase-activating polypeptide and VIP from R. ridibunda are members of the secretin/glucagon/vasoactive intestinal polypeptide superfamily and stimulate growth hormone release. Both pituitary adenylate cyclase-activating polypeptide and VIP affect wound healing. Frog and porcine VIP differ only in 4 aa; only one aa is different in the frog and mammalian sequence of pituitary adenylate cyclase-activating polypeptide.324−327 VIPs generally have 28 aa with an amidated C-terminus; however, NVRPs 1−4 from the red-bellied newt Cynops pyrrhogaster have 30 aa and a free Cterminus.177 V


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Table 11. Immunomodulatory Peptides from Amphibiansa name

sequence

bioactivities

species/ref

esculentin-2Cha temporin A brevinin-2GU B2RP-Era [D4k]ascaphin-8 [G4K]XT-7 [T5k]temporin-DRa pYR pLR rothein 1 frenatin 2D frenatin 2.1D macrotympanain-A1 odorranain-A-OA11 andersonin-G1 margaratain-A1 margaratain-B1 andersonin-D1 odorranian-A-OA12 andersonin-H3 andersonin-N1 andersonin-Q1 andersonin-R1 andersonin-S1 lividin-D1 schmackerin-C1 tiannanin-A1 wuchuanin-C1 wuchuanin-D1 wuchuanin-F1 dermaseptin S9

GFSSIFRGVAKFASKGLGKDLAKLGVDLVACKISKQC FLPLIGRVLSGIL GVIIDTLKGAAKTVAAELLRKAHCKLTNSC GVIKSVLKGVAKTVALGML-NH2 GFKkLLKGAAKALVKTVLF-NH2 GLLKPLLKIAAKVGSNLL-NH2 HFLGkLVNLAKKIL-NH2 YLKGCWTKSYPPKPCFSR-NH2 LVRGCWTKSYPPKPCFVR-NH2 SVSNIPESIGF DLLGTLGNLPLPFI-NH2 GTLGNLPAPFPG FLPGLECVW VVKCSYRLGSPDSQCN KEKLKLKAKAPKCYNDKLACT VTPPWARIYYGCAKA FFSTSCRSGC FIFPKKNIINSLFGR VVKFSYRKGSPAPQKN VAIYGRDDRSDVCRQVQHNWLVCDTY ENMFNIKSSVESDSFWG QMFHLWYLRHMKNKKPMA ENAEEDEVLMENLFCSYIVGSADSFWT DANVENGEDAEDLTDKFIGLMG KNNFCQVLYVWLLRLGKQCFVKFSKDVET AAPRGGKGFFCKLFKDC LLPPWLRPRNG VFLGNIVSMGKKI DAAVEPELYHWGKVWLPN VADKRPYILREKKSIPY GLRSKIWLWVLLMIWQESNKFKKM

increasing IL-10 chemoattracting phagocytes affecting release of cytokines affecting release of cytokines affecting release of cytokines affecting release of cytokines affecting release of cytokines inhibiting macrophage development inhibiting macrophage development lymphocyte proliferator stimulating cytokines stimulating cytokines inhibiting TNF-α increasing IL-8 increasing IL-8 increasing IL-8 inhibiting TNF-α, increasing IL-8 increasing TNF-α inhibiting IL-8 inhibiting IL-8 inhibiting IL-8 inhibiting IL-8 inhibiting IL-8 inhibiting IL-8 inhibiting IL-8 inhibiting IL-8 inhibiting IL-8 inhibiting IL-8 inhibiting IL-8 inhibiting IL-8 chemoattractant activities

LC328 RT331 HG330 HG330 AT330 ST330 RD330 RS201 LP206 LRO95 DS329 DS329 OM275 OA275 OA275 OM275 OM275 OA275 OA275 OA275 OA275 OA275 OA275 OA275 OL275 OS275 OT275 OW275 OW275 OW275 PS332

a

AT, Ascaphus truei; DS, Discoglossus sardus; HG, Hylarana guentheri; LC, Lithobates chiricahuensis; LP, Lithobates pipiens; LRO, Litoria rothii; OA, Odorrana andersonii; OL, Odorrana livida; OM, Odorrana macrotympana; OS, Odorrana schmackeri; OT, Odorrana tiannanensis; OW, Odorrana wuchuanensis; PS, Phyllomedusa sauvagei; RD, Rana draytonii; RS, Rana sevosa; RT, Rana temporaria; ST, Silurana tropicalis.

2.12. Immunomodulatory Peptides

nanin-A1, wuchuanin-C1, wuchuanin-D1, and wuchuaninF1.275 Also, some peptides from amphibians affect the function of immunocytes. For example, natural pYR and pLR inhibit the early development of granulocyte macrophage colonies from bone marrow stem cells.201,206 In contrast to pYR and pLR, temporin A and related peptides induce human macrophages, monocytes, and neutrophils to migrate in a pertussis toxinsensitive manner. The mechanism involves activating p44/42 mitogen-activated protein kinase, and stimulates Ca2+ flux both in monocytes in vitro and in vivo through the G proteincoupled receptor FPRL1.331 In contrast to the inhibition of macrophages by pYR and pLR, rothein 1 is a lymphocyte proliferator that acts via the CCK2 receptor. Increasing the Nterminal hydrophobic properties of rothein 1 enhances lymphocyte activity, while replacing the hydrophilic groups E7 or S8 or the C-terminal F with A leads to loss of activity. This finding indicates that both hydrophilic and hydrophobic interactions between CCK2 receptor and rothein 1 are important for its lymphocyte proliferation activity.95

Some amphibian skin peptides such as esculentin-2CHa, frenatin 2D, andersonin-D1, and B2RP-Era can alter production of cytokines (Table 11). Esculentin-2CHa induces release of proinflammatory TNF-α mouse from peritoneal macrophages and anti-inflammatory IL-10 from lymphoid cells.328 Similarly, frenatin 2D induces mouse peritoneal macrophages to significantly produce TNF-α, IL-1β, and IL12 and weakly enhances unstimulated cells to generate IL-6.329 [T5K] temporin-DRa and B2RP-ERa clearly increase antiinflammatory TGF-β, IL-4, and IL-10 in the supernatant of both concanavalin A-treated and unstimulated peripheral blood mononuclear cells.330 IL-8 release can be significantly increased by andersonin-G1, odorranain-A-OA11, margaratain-A1 and -B1.275 Contrary to esculentin-2CHa, macrotympanain-A1 and margaratain-B1 inhibit TNF-α production induced by lipopolysaccharide (LPS) [G4K]XT-7, [D4K]ascaphin-8, brevinin-2GU, and [T5K]temporin-DRa, and B2RP-ERa also markedly decreases TNF-α release from concanavalin Astimulated peripheral blood mononuclear cells. Furthermore, [D4K]ascaphin-8 and brevinin-2GU clearly reduce IFN-γ release from unstimulated peripheral blood mononuclear cells.330 IL-8 release is significantly inhibited by andersoninH3, andersonin-N1, andersonin-Q1, andersonin-R1, andersonin-S1, odorranian-A-OA12, lividin-D1, schmackerin-C1, tian-

2.13. Neuronal Nitric Oxide Synthase Inhibitors

Lesueurin from the skin secretions of the frog L. lesueuri is the first amphibian peptide found to inhibit neuronal nitric oxide synthase (nNOS).141 Many peptides with nNOS inhibition function have now been identified from the glandular secretions of Litoria and Crinia frogs, although these basic amphibian W


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Table 12. nNOS Inhibitors from Amphibians name Group 1 lesueurin aurein 1.1 citropin 1.1 citropin 1.2.3 uperin 3.6 aurein 2.2 aurein 2.3 aurein 2.4 signiferin 2.1 Group 2 caerin 1.1 caerin 1.10 caerin 1.20 caerin 1.6 caerin 1.8 caerin 1.8.1 caerin 1.9 caerin 1.19 caerin 1.19.3 Group 3 signiferin 3.1 citropin 2.1 signiferin 4.3 splendipherin aurein 5.2 frenatin 3 caerin 2.6 dahlein 5.2 dahlein 5.3 dahlein 5.1 dahlein 5.6 Group 4 fallaxin 3 dahlein 4.2 deserticolin 1

sequence

IC50 (μM)

charge

GLLDILKKVGKVA-NH2 GLFDIIKKIAESI-NH2 GLFDVIKKVASVIGGL-NH2 GLFDIIKKVAS-NH2 GVIDAAKKVVNVLKNLF-NH2 GFLDIVKKVVGALGSL-NH2 GFLDIVKKVVGIAGSL-NH2 GLFDIVKKVVGTLAGL-NH2 IIGHLIKTALGMLGL-NH2

16.2 33.9 8.2 20.5 4.4 4.4 1.8 2.4 16.6

+3 +1 +2 +2 +3 +2 +2 +2 +2

L. lesueuri L. aurea L. citropa L. citrop U. mjobergi L. aurea L. aurea L. aurea C. signifera

141 339 340 340 340 339 339 339 254

GLLGVLVSIAKHVLPHVVPVIAEHL-NH2 GLLSVLGSVAKHVLPHVVPVIAEKL-NH2 GLFGILGSVAKHVLPHVIPVVAEHL-NH2 GLFSVLGAVAKHVLPHVVPVIAEKL-NH2 GLFKVLGSVAKHLLPHVVPVIAEKL-NH2 GSVAKHLLPHVVPVIAEKL-NH2 GLFGVLGSIAKHVLPHVVPVIAEKL-NH2 GLFKVLGSVAKHLLPHVAPIIAEKL-NH2 GSVAKHLLPHVAPIIAEKL-NH2

36.6 41 27.2 8.4 1.7

+1 +2 +1 +2 +3 +2 +2 +3 +2

L. L. L. L. L. L. L. L. L.

341 141 141 141 141, 342 252 342,343 342, 343 342, 343

GIAEFLNYIKSKA-NH2 GLIGSIGKALGGLLVDVLKPKL GFADLFGKAVDFIKSRV-NH2 GLVSSIGKALGGLLADVVKSKGQPA GLMSSIGKALGGLIVDVLKPKTPAS GLMSVLGHAVGNVLGGLFKPKS GLVSSIGKVLGGLLADVVKSKGQPA GLLGSIGNAIGAFIANKLKPK GLLASLGKVLGGYLAEKLKP GLLGSIGNAIGAFIANKLKP GLLASLGKVFGGYLAEKLKPK

81.2 31.2 16.6 9.1 7.7 6.8 6.6 2.6 1.4 3.2 1.6

+2 +3 +2 +2 +2 +2 +2 +3 +2 +3 +3

C. signifera, C. riparia L. citropa C. signifera L. splendida L. aurea L. infrafrenata hybrid L. dahlia L. dahlia L. dahlia L. dahlia

254 141 252 98 344 342 345 346 346 346 346

GLLSFLPKVIGVIGHLIHPPS-NH2 GLWQFIKDKIKDAATGLVTGIQS-NH2 GLADFLNKAVGKVVDFVKS-NH2

15.4 11.1 2.4

+3 +2 +2

L. fallax L. dahlii C. deserticola

347 348 252

6.2 3.9

peptides show little sequence homology with Ca2+/calmodulin (CaM), the Ca2+/ CaM-binding domain of nNOS, or other peptides or proteins that inhibit nNOS (Table 12). Peptides that inhibit nNOS are often the main active constituents of skin secretions and are classified into four categories: (1) citropin 1 peptides, most of which contain amphipathic α-helices, have 16 aa and show potent antimicrobial and anticancer activities with the exception of lesueurin; (2) caerin 1 peptides, which contain F3 with a helix-hinge-helix structure and have no antimicrobial or anticancer activity; (3) frenatin/splendipherin peptides, most of which contain two adjacent G residues toward the center and two K residues near the C-terminus and have potent membrane activity with the exception of dahlein 5.2; helixes of frenatin-like peptides are disrupted by two sequential central G residues that are absent in dahlein 5.2 because G at the end of helical regions is a secondary structure breaker; and (4) peptides that do not fall into the above groups but inhibit nNOS function. The NO signaling molecule has many functions in animals and affects nerve, muscle, immunity, and cardiovascular systems. In anurans, NO is involved in reproduction, sight, and modulation of gastric acids. NO is regulated by three distinct isoforms of NOS in every cell type.141,333,334 NOS has a

species

ref

caerulea chloris caerulea chloris chloris chloris chloris gracilenta gracilenta

catalytic oxygenase domain, an electron-supplying reductase domain, and an intervening CaM binding region. The amphipathic amphibian peptides inhibit nNOS by changing the shape of a cofactor or interacting with Ca2+/CaM, hindering its interaction with the CaM-docking site on nNOS and electron transfer from cofactors to heme in the reductase domain during NO formation. This mechanism is confirmed by evidences: (1) nNOS is inhibited and NO production is decreased when the peptides are added to nNOS in vitro, and nNOS activity can be partially recovered by adding Ca2+/CaM; (2) the function of calcineurin, another enzyme using Ca2+/ CaM as a regulatory protein, is inhibited by frenatin 3 and citropin 1.1;141,335 and (3) caerin 1.8, citropin 1.1, dahlein 5.6, and spendipherin form globular complexes with Ca2+/CaM under electrospray ionization conditions.336−338 In addition, three-dimensional structures of frenatin 3 demonstrate amphibian peptide binding to Ca2+/CaM. An amphipathic αhelix of residues 1−14 forms in frenatin 3, whose 8 residues at the C-terminus are less structured and more flexible in trifluoroethanol/water mixture. Some α-helical character is seen in the frenatin 3 N-terminal region in water.335 X


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Table 13. AMPs from Alytes and Ascaphus Frogs source

name

sequence

A. obstetricans

ref 351

alyteserin-1a alyteserin-1b alyteserin-1c alyteserin-1d alyteserin-2a alyteserin-2b alyteserin-2c

GLKDIFKAGLGSLVKGIAAHVAN-NH2 GLKEIFKAGLGSLVKGIAAHVAN-NH2 GLKEIFKAGLGSLVKGIAAHVAS-NH2 GLKDIFKAGLGSLVKNIAAHVAN-NH2 ILGKLLSTAAGLLSNL-NH2 ILGAILPLVSGLLSNKL-NH2 ILGAILPLVSGLLSSKL-NH2

alyteserin-2M alyteserin-2Mb alyteserin-1Ma alyteserin-1Mb alytesin

FIGKLISAASGLLSHL-NH2 ILGAIIPLVSGLLSHL-NH2 GFKEVLKADLGSLVKGIAAHVAN-NH2 GFKEVLKAGLGSLVKGIPAHVAN-NH2 pQGRLGTQWAVGHLM-NH2

ascaphin-1 ascaphin-2 ascaphin-3 ascaphin-4 ascaphin-5 ascaphin-6 ascaphin-7 ascaphin-8

GFRDVLKGAAKAFVKTVAGHIAN-NH2 GFRDVLKGAAKQFVKTVAGHIAN GFRDVLKGAAKAFVKTVAGHIANI GFKDWIKGAAKKLIKTVAANIANQ GIKDWIKGAAKKLIKTVASHIANQ GFKDWIKGAAKKLIKTVASSIANE GFKDWIKGAAKKLIKTVASSIANQ GFKDLLKGAAKALVKTVLF-NH2

ascaphin-1M ascaphin-3M ascaphin-4M ascaphin-5Ma ascaphin-5Mb ascaphin-7M

GFRDVLKGAAKEFVKTVAGHIAN-NH2 GFREVLKGAAKAFVKTVAGHIANI GFKDWIKGAAKKLIKTVASNIANQ GIKDWIKGAAKKLIKTVASHIANQ GIKDWIKGAAKTLIKTVASHIANQ GFKDWIKSAAKKLIKTVASNIANQ

A. maurus

355

A. truei

357

A. montanus

358

nosocomial pathogen Acinetobacter baumannii.352,353 Alyteserin2 peptides are preferential against Gram-positive bacteria such as S. aureus, which has low hemolytic activity.351 The increase in positive residues in alyteserin-2a while maintaining amphipathicity by replacing G11 with K enhances its potency against both Gram-positive and Gram-negative bacteria by 4−16-fold. However, this substitution also produces a 6-fold increase in hemolytic activity against human erythrocytes. Additional replacement of S7 with K further enhances antimicrobial potency without increasing cytotoxicity to erythrocytes. The peptide containing D-Lys at positions 7 and 11 has high potency against a broad spectrum of Gram-negative bacteria and appreciably lowers hemolytic activity and cytotoxicity against A549 cells.354 Four alyteserin peptides identified from A. maurus also have antimicrobial effects. Precursor cDNA from A. maurus resembling those from Bombinatoridae in both structural architecture and translated aa sequence encodes AMPs as tandem repeats, with alyteserin-1Ma or alyteserin1Mb followed by alyteserin-2Ma or alyteserin-2Mb. In addition, alytesin has been identified in A. maurus, and the cDNA encoding its precursor is identical in sequence to bombesinrelated peptides from other frogs.355 2.14.2. Ascaphus. The Ascaphus tailed frogs are the most primitive extant anurans and include A. montanus, which lives in inland ranges, and A. truei, which are coastal range frogs.356 Ascaphins 1−8 have broad-spectrum antimicrobial activities and have been purified from norepinephrine-stimulated skin secretions of A. truei (Table 13).357 These structurally similar peptides might originate from multiple duplications of an

2.14. Antimicrobial Peptides from Amphibian Skin Secretions

The humid skin of amphibians usually makes them dependent on habitats in or near water or in wetlands with many microbial pathogens. Amphibians have a poor cell-mediated adaptive immune system against pathogens. Thus, innate immune defenses like AMPs are important for preventing infection. Amphibian skin is the firstline defense against microbial infection. AMPs in the outer layer of amphibian skin prevent infection. A diverse array of AMPs 10−50 residues long is synthesized and released by the granular skin glands of anuran amphibians to provide an effective and fast-acting defense against microorganisms.349,350 We describe about 1900 AMPs from 178 amphibian species belonging to 28 genera in this Review (Tables 13−27). The 1900 AMPs can be structurally classified into about 100 families, although some peptide families have varied nomenclature. Considering the nomenclature complexity of AMPs in different amphibian species, we described AMPs according to their sources. 2.14.1. Alytes. AMPs have been identified from two amphibian species in the genus Alytes (Table 13). Two families of AMPs that are structurally related and contain α-amidated Ctermini have been reported in skin secretions of the toad A. obstetricans.351 Both alyteserin-1 and alyteserin-2 peptides have restricted identity to the ascaphins and to bombinin H6 from Leiopelmatidae and Bombinatoridae frogs. Alyteserin-1 peptides selectively inhibit the growth of Gramnegative bacteria with weak hemolytic activity. Alyteserin-1c and its [E4K] analog inhibit multidrug-resistant strains of the Y


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Table 14. AMPs from Bombina Toads source

name

sequence

B. maxima

ref 6−10, 48, 231, 362, 365, 371, 372

maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 H1 H2 H3 H4 H5 H6 H7 H8 H9 H10 H11 H12 H13 H14 H15 H16 H17 H18 H19 H20 H21 H23 Hv Hu Ht Hw S5 S4 S3 S2 S1 56 62 63

GIGTKILGGVKTALKGALKELASTYAN GIGTKILGGVKTALKGALKELASTYVN GIGGKILSGLKTALKGAAKELASTYLH GIGGVLLSAGKAALKGLAKVLAEKYAN SIGAKILGGVKTFFKGALKELASTYLQ GIGGALLSAGKSALKGLAKGLAEHFAN GIGAKILGGVKTALKGALKELASTYVN GIGTKILGGLKTAVKGALKELASTYVN GIGRKFLGGVKTTFRCGVKDFASKHLY-NH2 GIGGALLSAGKSALKGLAKGLAEHFAS GIGTKIIGGLKTAVKGALKELASTYVN GIGGKILSGFKTALKGAAKELAFTYLH GIGGVLLSAGKAALKGLAKVLAEKYAD GIGGALLSAGKSALKGLAKGLADHFAN GIGTKILGGVKAALKGALKELASTYVN DIGTKILGGVKTALKGALKELASTYVN GIGTKILGGVKTALKGALKELASTYV GIGTKILGGVKTALKGALKELAFTYAN GIGTKILGGVKTALKGALKELAFTYAN GIGTKILGGVKTALKGALKELAFTYVN GIGTKIIGGLKTAVKGALKELASTYVN GIGTKIIGGLKTAVKGALKELVFTYVN GIGTKIVGGFKTGDKKIFNELGWRYV GIGRKFLGGVKTTFRCGDKDFASKHLY GIGGKILSGLKTALKGAAKELASTYLH GIGGKILGGLKTALKGAAKELAATYLH ILGPVISTIGGVLGGLLKNL ILGPVLSMVGSALGGLIKKI ILGPVLGLVGNALGGLIKKI ILGPVISKIGGVLGGLLKNL ILGPVLGLVSDTLDDVLGIL-NH2 ILGPVIGTIGNVLGGLLKN ILGPVIKTIGGVIGGLLKN ILGPVLGLVSNALGGLLKNI ILGPVLGLVSNALGGLIKKI ILGPVLGLVSNALGGLLKNL ILGPVLGLVGSALGGLIKKI LLGPVLGLVSNALGGLLKNI ILGPVIKTIGGVLGGLLKNL ILGPVLGLVGEPLGGLIKKI ILGPVIGTTGNVLGGLLKNL ILGPVLSLVGNALGGLIKKI ILGPVLSLVGNALGGLIKKI ILGPVLSMVGSALGGFFKKI ILGPVLGLVGNPLGGLIKKI ILGPVLGLVGNALGGLLKNL ILGPVLGLVSNVLGGLL ILGPVISTIGNVLGGLLKNL ILGPVLSLVGSALGGLIKKI ILGPVLSLVGNALGGLLKNE ILGPVLGLVGNALGGLIKNE ILGPVLGLVSNAIGGLIKKI GSNKGFNFMVDMIQALSK-NH2 RSNKGFNFMVDMIQALSK-NH2 GSNKGFNFMVDMINALSN-NH2 GSNKGFNFMVDMIQALSN-NH2 GSNTGFNFKTLDKE GIGTKIIGGLKTAVKGALKELAFTYVN GIGGKILSGFKTALKGAAKELAATYLH GIGGVLLGAGKATLKGLAKVLAEKYAN Z


Chemical Reviews

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Table 14. continued source

name

sequence

maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin

64 65 66 67 68 69 70 71 72 73 74 75 H37 H38 H39 H40 H41 H42 H43 H44 H45 H46 H47

GIGTKIIGGLKTAVKGALKESAFTYVN GIGGKILFGLKTALKGAAKELAATYLH GIGGKILSGLKTALKGAAKELAATYLH GIGGALLSAGKAALKGLAKVLAEKYAN GIGGALLSAGKAALKGLAKVLV GIGGKILGGVKTALKGALKELASTYAN GIGGKILPGFKTALKGAAKELAATYLH GIGGVLLSAGKAALKGLARVLAEKYAN GIGTKIIGGFKTAVKGALKELAFTYVN GIGTKILGGVKTALKGALKELAPTYVN GIGTRIIGGLKTAVKGALKELASTYVN SIGAKILGGVKTFFKGALKELAFTYLQ ILGPVLGLVSNTLDDVLGIL ILGPVLGLVGNALGGYLKIL ILGPVLGLVGNALGGLIKKL ILGPVLGLIGNALGGLIKKI ILGPVLGLVSGTLDDVLGIL VLGPVLGLVSNALGGLL ILGPVLGLVDNALGGLIKKI ILGPVLGLVGNALGGLIKEI ILGPVLGLVGNDLEVYLKI ISGPVLGLVGNALGGLIKKI LLGPVLGLVSNDLEVYLKIL

maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin

1 2 4 5 6 7 10 11 26 27 28 29 30 31 32 33 34 36 37 38 39 41 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57

GIGTKILGGVKTALKGALKELASTYAN GIGTKILGGVKTALKGALKELASTYVN GIGGVLLSAGKAALKGLAKVLAEKYAN SIGAKILGGVKTFFKGALKELASTYLQ GIGGALLSAGKSALKGLAKGLAEHFAN GIGAKILGGVKTALKGALKELASTYVN GIGGALLSAGKSALKGLAKGLAEHFAS GIGTKIIGGLKTAVKGALKELASTYVN GIGGKILGGLKTALKGAAKELAATYLH GIGGKILAGVKTALKGAAKELAATYLH GIGTKFLGGVKTALKGALKELASTYVN GIGGKILGGFKTALKGAAKELAATYLH GIGGAILSAGKSALKGLAKGLAEHF GIGGALLSAGKSALKGLAKGLAEHF GIGGKILGGLKTALKGAAKELASTYLH GIGGKILGGLKTALKGAAKELAATYLQ GIGTKFLGGLKTAVKGALKELASTYVN GIGGALLSVGKSALKGLAKGLAEHF GIGGKILGGLKTALKGAAKELAFTYLH GIGGKILGGPKTALKGAAKELASTYLH GIGTKFLGGVKTALKGALKELAFTYVN GIGGALLSVGKSALKGLTKGLAEHF GIGGKILGGLKTALKGAAKELASTYQH GIGGKILGGLKTVLKDAAKELAATYLH GIGGKILGGLRTALKGAAKELAATYLH GIGGKILSGLKTALKGAAKQLAATYLH GIGGRILGGLKTALKGAAKELAATYLH GIGGVLLCAGKAALKGLAKVLAEKYAN GIGGVLLSAGKAALKGLTKVLAEKYAN GIGGVLLSAGKAALKGLVKVLAEKYVN GIGGVLPSAGKAALKGLAKVLAEKYAN GIGRKILGGLKTALKGAAKELAATYLH GIGTKFLGGLKTAVKGALKELAFTYVN GIGTKFLGGLKTAVKGALKELASTYVS GIGTKFLGGLKTAVKGALKELASTYVY GIGTKIIGGLKTAVKGALKELAFTYVN IGAKVLGGVKTFFKGALKELASTYQQ

B. microdeladigitora

ref

362

AA


Chemical Reviews

Review


name maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin maximin

sequence

58 61 68 75 76 77 78 H1 H3 H4 H7 H8 H9 H10 H11 H15 H16 H23 H24 H25 H26 H27 H28 H29 H30 H31 H32 H33 H34 H35 H36 H48 H49 H50 H51 H52 H53

ref

GIGGALLSAGKSALKGVAIGLAEHFAN GIGGALLSVGKSALKDLAKGLAEHF GIGGALLSAGKAALKGLAKVLV GIGTKILGGVKTALKGALKGLASTYAN GIGGALLSAGKSALKGLAKVLADKFAN GIGGALLSAGKSALKGLAKGLAEHL GIGGALLSVGKLALKGLANVLADKFAN ILGPVISTIGGVLGGLLKNL ILGPVLGLVGNALGGLIKKI ILGPVISKIGGVLGGLLKNL ILGPVIKTIGGVIGGLLKNL ILGPVLGLVSNALGGLLKNI ILGPVLGLVSNALGGLIKKI ILGPVLGLVSNALGGLLKNL ILGPVLGLVGSALGGLIKKI ILGPVLGLVGNALGGLLKNL ILGPVLSLVGNALGGLIKKI ILGPVISTIGNVLGGLLKNL ILGPVLGLVGDTLGDLL ILGPVLGLVGSALGGLLKNL ILLPVLGLVGNALGGLLKNL ILGPVLGLVSNALGGLL ILGPVLGLAGNALGGLIKKI ILGPVLGLDSNALEGLIKKI ILGPVLGLVDSALGGLLKYL ILGPVLGLVGSVLGGLLKNL ILGPVLGLVSNALGGLI ILGPVLGLVGNTLGGLIKKI ILGPVVGLVGNALGGLLKNL ILGSVLGLVGNALGGLIKKI IMGPVLGLVSNALGGLLKNL ILGPVLGLVGSALGGLI VLGPVLGLASNALGGLIKKI ISGPVLGLVGSALGGLIKKI ILGPVLGLVSNALDDVLGIL ILGLVISTIGNVLGGLLKNL ILGPALGLVGNALGGLLKNL

B. orientalis

364, 366 bombinin-like bombinin-like bombinin-like bombinin-like bombinin-like

peptide peptide peptide peptide peptide

1 2 3 4 7

GIGASILSAGKSALKGLAKGLAEHFAN-NH2 GIGSAILSAGKSALKGLAKGLAEHFAN-NH2 GIGAAILSAGKSALKGLAKGLAEHFG-NH2 GIGAAILSAGKSIIKGLANGLAEHF-NH2 GIGGALLSAGKSALKGLAKGLAEHFAN

B. variegata

118, 294, 363, 370 bombinin bombinin-H bombinin-H1/H3 bombinin-H4 bombinin-like peptide 1 bombinin-like peptide 2 bombinin-H6 bombinin-H7

GIGALSAKGALKGLAKGLAZHFAN IIGPVLGLVGSALGGLLKKI-NH2 IIGPVLGMVGSALGGLLKKIG IIGPVLGLVGSALGGLLKKI-NH2 GIGGALLSAAKVGLKGLAKGLAEHFAN GIGASILSAGKSALKGFAKGLAEHFAN ILGPILGLVSNAGGLL-NH2 ILGPILGLVSNALGGLL-NH2

ascaphin-8 have α-amidated C-termini. Ascaphin-1, ascaphin3, ascaphin-4, ascaphin-5, and ascaphin-7 isolated from tailed frogs from A. montanus contain 1−2 aa from compared A. truei orthologs. This result is consistent with the population assignment of Ascaphus.358 Secretion from A. montanus does not contain orthologs of ascaphin-2, ascaphin-6, or ascaphin-8. The ascaphins have a wide range of antimicrobial activities with

ancestral gene and do not closely resemble AMPs from the skins of other frog species. Ascaphins show low sequence homologue to the amphipathic, cationic α-helical peptides opistoporin 1 and pandinin 1 from African scorpion venome. This might be coincidental and not an evolutionary relationship. Ascaphins 2−7 are represented by the consensus sequence GXXDXXKGAAKXXXKTVAXXIANX, and ascaphin-1 and AB


Chemical Reviews

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Table 15. AMPs from Hoplobatrachus and Kassina Frogs source

name

sequence

H. tigerinus

H. rugulosus F. cancrivora

ref 373

tigerinin-1 tigerinin-2 tigerinin-3 tigerinin-4 tigerinin-1R

FCTMIPIPRCY-NH2 RVCFAIPLPICH-NH2 RVCYAIPLPICY-NH2 RVCYAIPLPIC-NH2 RVCSAIPLPICH-NH2

tigerinin-RC1 tigerinin-RC2

RVCSAIPLPICH RVCMAIPLPLCH

kasseptin 2Ma kasseptin 2Mb kasseptin 2Mc kasseptin 2Md kassorin M

FLGAIAAALPHVINAVTNAL-NH2 FFGAIAAALPHVISAIKNAL-NH2 FVGAIAAALPHVISAIKNAL-NH2 IIGAIAAALPHVINAIKNTF-NH2 FLEGLLNTVTGLL-NH2

galensin kassinatuerin-1 kassinatuerin-2 kassorin S

AAEEERNVEKRCYSAAKYPGFQEFINRKYKSSRFG GFMKYIGPLIPHAVKAISDLI-NH2 FIQYLAPLIPHAVKAISDLI-NH2 FLGGILNTITGLL-NH2

K. maculata

286 374

308, 377

K. senegalensis

292, 308, 376

strong potential against Gram-negative bacteria.357 For example, ascaphin-8, which contains an amphipathic α-helical conformation in membrane-mimetic environments, inhibits the growth of a range of clinical isolates of Escherichia coli and Klebsiella pneumoniae strains with relatively high potency (minimum inhibitory concentration (MIC) < 25 μM). The therapeutic potential of ascaphin-8 is restricted by hemolytic activity (LC50 = 55 μM). Some analogs without toxicity against human erythrocytes and potency against microorganisms have been designed.359 Analogs that increase cationicity while maintaining amphipathicity by replacement of A10, V14, and L18 with L-Lys or D-Lys retain potency against a range of microorganisms but decrease toxicy against human cells by 10fold. The reducion in toxicity against mammal cells of the LLys18 and D-Lys18 analogs is associated with a decrease in their effective hydrophobicity and α-helix structure.359 K4 and K8 analogs generally contain the most potent activities against bacteria and erythrocytes. However, K10, K14, and K18 analogs also show potent antibacterial activity with very low hemolytic activity.360 Thus, analogs of ascaphin-8 whose antimicrobial properties in part correlate with their action against ATP synthase are promising for the development of a therapeutically valuable anti-infective agent.361 2.14.3. Bombina. Many AMPs have been identified from skin secretions of toads in the genus Bombina. In particular, more than 80 AMPs are reported in B. maxima (Table 14).362 On the basis of structural similarity, these peptides are classified into two families: bombinins and bombinins H. Bombinin was the first AMP isolated from B. variegata based on its hemolytic activity.118 Subsequently, bombinin-like peptides were isolated from B. maxima, B. orientalis, and B. variegata.363−365 Bombinin H peptides were first found by analysis of the nucleotide sequences of the biosynthetic precursors of the bombinins and were purified from skin secretions of B. maxima, B. variegata, and B. orientalis.366−368 Bombinin H peptides are mildly cationic and hydrophobic AMPs rich in G (25%) residues, allowing structural polymorphism. Environmental conditions can trigger self-aggregation of bombinin H in solution through hydrophobic interaction. Bombinin H6 from B. maxima and

bombinin H3 and H4 from B. variegata contain D-allo-Ile or DLeu substitutions at position 2 from posttranslational modification by an isomerization enzyme. This change makes H4 less constrained and more flexible than L-aa substitutions at position 2.147,367,369,370 In addition, a peptide termed maximin H5 contains unusually three D residues and no basic aa.368 Unlike most of the amphibian AMPs, the precursors of maximin S peptides from B. maxima contain maximin S1 and different combinations of tandemly repeated maximin S2−S5, separated by internal peptides.371 In general, bombinins are active against Gram-negative bacteria, Gram-positive bacteria, and fungi but virtually inactive against erythrocytes. Conversely, bombinin H peptides have lower bactericidal activities but higher hemolytic activity. Maximin 9 is a free thiol containing AMP from B. maxima that has antimycoplasma activity. However, S. aureus, E. coli, Bacillus pyocyaneus, and C. albicans are resistant to maximin 9, its homodimer, and the C16-G16 analog.372 In contrast to maximin and maximin H peptides that strongly inhibit the growth of broad-spectrum microorganisms, antimicrobial tests showed that only maximin S4 among the maximin S peptides has activity against clinical mycoplasma strains; it has no activity against common Gram-negative or Gram-positive bacteria or fungal strains tested.371 The D-aa analogs are more potent than the all L-aa peptides. In addition, bombinins H6 and H7 with more hydrophobicity have weak antimicrobial activity against Aeromonas hydrophiliai, which causes the generally fatal red leg disease in frogs.367 The anionic maximin H5 has only low antimicrobial activity against S. aureus.368 2.14.4. Hoplobatrachus. The Indian frog H. tigerinus formerly named R. tigerina in the family Ranidae contains 11and 12-residue tigerinins with activity against a range of microorganisms (Table 15). In addition to containing an αamidated C-terminus and being among the shortest AMPs isolated from animal sources, tigerinins also contain a nonapeptide ring forming an intramolecular disulfide bridge.373 Conformational analysis showed that the tigerinins are mixtures of unordered and β-turn conformations.373 The cDNAs encoding the tigerinin-RC1 and tigerinin-RC2 precursors AC


Chemical Reviews

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Table 16. AMPs from Leptodactylus Frogs source L. fallax L. ocellatus

name

sequence

fallaxin/ocellatin-F1

GVVDILKGAAKDIAGHLASKVMNKL-NH2

ocellatin-1 ocellatin-2 ocellatin-3 ocellatin-4 ocellatin-5

GVVDILKGAGKDLLAHLVGKISEKV-NH2 GVLDIFKDAAKQILAHAAEQI-NH2 GVLDILKNAAKNILAHAAEQI-NH2 GLLDFVTGVGKDIFAQLIKQI-NH2 GLLDFLKAAGKGLVTNL

leptoglycin pentadactylin/ocellatin-P1 syphaxin/ocellatin-S1

GLLGGLLGPLLGGGGGGGGGLL GLLDTLKGAAKNVVGSLASKVMEKL-NH2 GVLDILKGAAKDLAGHVATKVINK-NH2

ocellatin-V1 ocellatin-V2 ocellatin-V3

GVVDILKGAGKDLLAHALSKLSEKV-NH2 GVLDILKGAGKDLLAHALSKISEKV-NH2 GVLDILTGAGKDLLAHALSKLSEKV-NH2

laticeptin/ocellatin-L1 plasticin-L1 ocellatin-L2

GVVDILKGAAKDLAGHLATKVMNKL-NH2 GLVNGLLSSVLGGGQGGGGLLGGIL GVVDILKGAAKDLAGHLATKVMDKL-NH2

L. pentadactylus

L. syphax L. validus

ref 383 379, 384

385

L. laticeps

382 380, 386

378, 381, 386

are above 50 μM. Furthermore, these peptides have low or no hemolytic activity, except for ocellatin 4, which has a strong cytolytic activity but weaker antimicrobial activity. Ocellatin 4 has two positively charged and two negatively charged residues. In addition, it has an amidated C-terminal that self-associates in solution and a neutral charge at physiological pH. These features result in its strong hemolytic activity and favor interaction with zwitterionic phospholipids in mammalian plasma membranes.379 As compared to other active ocellatin peptides from related species, ocellatin-V1, ocellatin-V2, ocellatin-V3, and laticeptin lack amphipathicity and have reduced cationicity, which probably explains their low antimicrobial potency (MIC > 200 μM) against E. coli and S. aureus.380,381 Although syphaxin has an amidated C-terminus and 84% sequence identity to laticeptin, it has low activity against S. aureus and E. coli. Two peptides among six other truncated forms of syphaxin characterized from skin secretions of L. syphax have distinct potencies and low MIC values.382 2.14.7. Litoria. Frogs in the genus Litoria synthesize a range of AMPs belonging to six families based on their structural similarity: the aureins, caerins, citropins, dahleins, maculatins, and fallaxidins (Table 17). These peptides share some common characteristics. First, they are cationic and generally shorter than 25 residues, which is not long enough to span the bacterial membrane. Second, most contain a G residue at the N-terminus and an amidated C-terminus that are derived from posttranslational modification and are important for activity. Third, aureins 1−3, dahlein 1.2, citropins 1, and maculatin 2.1 possess at least two positive residues at positions 7 and 8 and adopt well-defined α-helical conformations in a membrane-mimetic solvent, structures that are essential for high antimicrobial ability.336 The common D4 is not important for antimicrobial activity because replacement of D4 with A does not markedly affect activity. The amphipathic α-helical caerin 1 and maculatin 1 from Litoria have a helix-hinge-helix structure in which the central hinge is essential for activities because removal of the central hinge of caerin 1 by replacement of P15 and P19 residues by A leads to a nonamphipathic α-helical peptide that lacks membrane activity.387 Caerins 1.1.3 and 1.1.5 have the residues of the first two helixes of caerin 1.1, while some peptides such

have remarkable structural identity with tigerinins from the Chinese frog Fejervarya cancrivora.374 Also, a tigerinin-related peptide was purified from H. rugulosus skin extracts; this peptide is also C-terminally α-amidated, which might be essential for maintaining potent antimicrobial activity in the tigerinins.286 In addition, although the loop structure of tigerinin 1 is important for optimal activity, loss of activity from loop structure damage can be compensated for to some extent by linearization and increased cationic charges.375 2.14.5. Kassina. AMPs in the skins of frogs classified into the genus Kassina are generally C-terminally amidated. Kassinatuerin-1 from skin extracts of K. senegalensis adopts an amphipathic α-helical conformation in a membrane-mimetic solvent and inhibits the growth of a range of microorganisms using strongly hemolytic activity.376 Replacement of the αamidated C-terminus of kassinatuerin-1 with a carboxylic acid group decreases potency against bacterial and erythrocytes by decreasing both cationicity and α-helicity. However, progressive substitutions of G7, S18, and D19 on the hydrophilic face of the α-helix with K to increase cationicity while maintaining the amphipathic α-helical character increase antimicrobial activity. Additionally, analogs with D-Lys at G7, S18, and D19 retain activity against Gram-negative bacteria and have decreased cytolytic activity. Similar to peptides with amidated C-terminal substitutions, the potency of kassinatuerin-1 against Grampositive bacteria and the yeast C. albicans is reduced because of the reduction in α-helicity.292 Kassinatuerin-2 from K. senegalensis does not inhibit the growth of E. coli and S. aureus.376 Four orthologs and kassorin M from K. maculata skin are active against S. aureus only.308,377 2.14.6. Leptodactylus. AMPs have been isolated from skin secretions of L. fallax, L. ocellatus, L. pentadactylus, L. syphax, L. validus, and L. laticeps, which are members of the ocellatin family (Table 16). Most of the AMPs show weak antimicrobial activity. For example, synthetic plasticin-L1 and ocellatin-L2 have no antimicrobial activities against any tested strains.378 Fallaxin and leptoglycin have low activity against Gram-negative bacteria, Gram-positive bacteria, and yeast. Although ocellatins and pentadactylin have antimicrobial activity against both Gram-negative and Gram-positive bacteria, their MIC values AD


Chemical Reviews

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Table 17. AMPs from Litoria Frogs source

name

sequence

L. aurea

ref 339

aurein 2.1 aurein 2.1.1 aurein 2.2 aurein 2.2.1 aurein 2.3 aurein 2.4 aurein 2.4.1 aurein 2.5 aurein 3.1 aurein 3.2 aurein 4.1 aurein 4.2 aurein 4.3 aurein 4.4 aurein 5.1 aurein 5.2 caerin 1 unnamed

GLLDIVKKVVGAFGSL-NH2 LDIVKKVVGAFGSL-NH2 GLFDIVKKVVGALGSL-NH2 FDIVKKVVGALGSL-NH2 GLFDIVKKVVGAIGSL-NH2 GLFDIVKKVVGTLAGL-NH2 FDIVKKVVGTLAGL-NH2 GLFDIVKKVVGAFGSL-NH2 GLFDIVKKIAGHIAGSI-NH2 GLFDIVKKIAGHIASSI-NH2 GLIQTIKEKLKELAGGLVTGIQS GLLQTIKEKLKEFAGGVVTGVQS GLLQTITEKLKEFAGGLVTGVQS GLLQTIKEKLKELATGLVIGVQS GLLDIVTGLLGNLIVDVLKPKTPAS GLMSSIGKALGGLIVDVLKPKTPAS GLFGILRSVAKHVLPHVVPVIAEHL-NH2

caerin caerin caerin caerin caerin caerin caerin caerin caerin caerin caerin caerin caerin caerin caerin caerin caerin caerin caerin caerin caerin caerin caerin caerin caerin caerin

1.1 1.1.1 1.1.2a 1.1.2 1.1.3a 1.1.3 1.1.4a 1.1.4 1.1.5 1.1.6a 1.2 1.3 1.4 1.5 1.6 1.7 1.20c 2.4 3.2 3.3 3.4 4.1 4.2 4.3 1.1.2 2.2

GLLSVLGSVAKHVLPHVVPVIAEHL-NH2 GLFSVLGSVAKHVVPRVVPVIAEHLG GLFSVLGSVAKHVVPRVVPVIAEHL GLFGILGSVAKHVLPHVVPVIAEHSG GLFGILGSVAKHVLPHVVPVIAEHS GLLSVLGSLKLIVPHVVPLIAEHLG GLLSVLGSLKLIVPHVVPLIAEHL SVLGKSVAKHLPHVVPVIAEKTG GLFGLAKGSVAKPHVVPVISQLVG GLFGLAKGSVAKPHVVPVISQLV-NH2 GLLGVLGSVAKHVLPHVVPVIAEHL-NH2 GLLSVLGSVAQHVLPHVVPVIAEHL-NH2 GLLSSLGSVAKHVLPHVVPVIAEHL-NH2 GLLSVLGSVVKHVLPHVVPVIAEHL-NH2 GLFSVLGAVAKHVLPHVVPVIAEKL-NH2 GLFKVLGSVAKHLLPHVAPVIAEKL-NH2 GLFGILGSVAKHVLPHVIPVVAEHL-NH2 GLVSSIGKALGGLLADVVKTKEQPA GLWEKIKEKASELVSGIVEGVK-NH2 GLWEKIKEKANELVSGIVEGVK-NH2 GLWEKIREKANELVSGIVEGVK-NH2 GLWQKIKSAAGDLASGIVEGIKS-NH2 GLWQKIKSAAGDLASGIVEAIKS-NH2 GLWQKIKQAAGDLASGIVEGIKS-NH2 GLLSVLGSVAKHVLPHVVPVIAEHLG GLVSSIGRALGGLLADVVKSKEQPA

caerin caerin caerin caerin

1.6 1.7 1.8 1.9

GLFSVLGAVAKHVLPHVVPVIAEK-NH2 GLFKVLGSVAKHLLPHVAPVIAEK-NH2 GLFKVLGSVAKHLLPHVVPVIAEK-NH2 GLFGVLGSIAKHVLPHVVPVIAEK-NH2

L. caerulea

388, 403

L. chloris

404

L. citropa

346 citropin citropin citropin citropin citropin citropin

1.1 1.1.3 1.2 1.3 2.1 2.1.3

GLFDVIKKVASVIGGL-NH2 GLFDVIKKVASVIGLASP-NH2 GLFDIIKKVASVVGGL-NH2 GLFDIIKKVASVIGGL-NH2 GLIGSIGKALGGLLVDVLKPKL-NH2 GLIGSIGKALGGLLVDVLKPKLQAAS

L. dahlii

348 dahlein 1.1 dahlein 1.2 dahlein 4.1

GLFDIIKNIVSTL-NH2 GLVFDIIKNIFSGL-NH2 GLWQLIKDKIKDAATGFVTGIQS AE


Chemical Reviews

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name dahlein dahlein dahlein dahlein dahlein dahlein dahlein dahlein

4.2 4.3 5.1 5.2 5.3 5.4 5.5 5.6

sequence

ref

GLWQLIKDKLKDAATGFVTGIQS GLWQLIKDKFKDAATGFVTGIQS GLLGSIGNAIGAFIANKLKP GLLGSIGNAIGAFIANKLKPK GLLASLGKVLGGYLAEKLKP GLLGSIGKVLGGYLAEKLKPK GLLASLGKVLGGYLAEKLKPK GLLASLGKVFGGYLAEKLKPK

L. eucnemis

285 caerin 1.11 maculatin 1.3 maculatin 1.4

GLLGAMFKVASKVLPHVVPAITEHF-NH2 GLLGLLGSVVSHVVPAIVGHF-NH2 GLLGLLGSVVSHVLPAITQHL-NH2

caeridin 7.1 uperin 7.1

GLLDMVTGLLGNL GWFDVVKHIASAV-NH2

fallaxidin fallaxidin fallaxidin fallaxidin fallaxidin fallaxidin fallaxidin fallaxidin fallaxidin fallaxidin

3.1 3.1.1 3.2 3.3 3.2.1 4.1 4.1a 4.2 5.1 5.2

GLLDLAKHVIGIASKL-NH2 LDLAKHVIGIASKL GLLDFAKHVIGIASKL-NH2 GLVDFAKHVIGIASKL-NH2 LDFAKHVIGIASKL GLLSFLPKVIGVIGHLIHPPS GLLSFLPKVIGVIGHLIPPS-NH2 GLFSFLPKVIGVIGHLIHPPS FLPLLASLVGGLLGKRS-NH2 FFRVLAKLGKLA

maculatin maculatin maculatin maculatin

1.1 1.2 2.1 3.1

L. ewingii

137

L. fallax

139

L. genimaculata

389, 405 GLFGVLAKVAAHVVPAIAEHF-NH2 GLFGVLAKVASHVVAAIAEHFQA-NH2 GFVDFLKKVAGTIANVVT-NH2 GLLQTIKEKLESLESLAKGIVSGIQA-NH2

L. gilleni

406, 407 caeridin caerin 1.1 caerin 1.4 caerin 2.2 caerin 2.5 caerin 3.1

GLFDAIGNLLGGLGL GLLSVLGSVAKHVLPHVVPVIAEHL-NH2 GLLSSLSSVAKHVLPHVVPVIAEHL GLVSSIGRALGGLLADVVKSKEQPA GLVASIGRALGGLLADVVKSKEQPA GLWQKIKDKASELVSGIVEGVK-NH2

caerin caerin caerin caerin

GLFSVLGSVAKHLLPHVAPIIAEKL-NH2 GLFSVLGSVAKHLLPHVVPVIAEKL-NH2 GLFKVLGSVAKHLLPHVAPIIAEKL-NH2 GLWEKVKEKANELVSGIVEGVK-NH2

L. gracilenta

343 1.17 1.18 1.19 3.5

L. infrafrenata

408 frenatin frenatin frenatin frenatin frenatin

1 2 3 3.1 4

GLLDALSGILGL-NH2 GLLGTLGNLLNGLGL-NH2 GLMSVLGHAVGNVLGGLFKPKS GLMSILGKVAGNVLGGLFKPKENVQKM GFLDKLKKGASDFANALVNSIKGT

L. raniformis

339 aurein aurein aurein aurein aurein aurein aurein aurein aurein aurein aurein

1.1 1.2 2.1 2.1.1 2.2 2.5 2.6 3.1 3.1.1 3.2 3.3

GLFDIIKKIAESI-NH2 GLFDIIKKIAESF-NH2 GLLDIVKKVVGAFGSL-NH2 LDIVKKVVGAFGSL-NH2 GLFDIVKKVVGALGSL-NH2 GLFDIVKKVVGAFGSL-NH2 GLFDIAKKVIGVIGSL-NH2 GLFDIVKKIAGHIAGSI-NH2 GLFDIVKKIAGHIAGSI FDIVKKIAGHIAGSI-NH2 GLFDIVKKIAGHIVSSI-NH2 AF


Chemical Reviews

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name

sequence

aurein aurein aurein aurein aurein

3.3.1 4.2 4.4 5.1 5.2

FDIVKKIAGHIVSSI-NH2 GLLQTIKEKLKEFAGGVVTGVQS GLLQTIKEKLKELATGLVIGVQS GLLDIVTGLLGNLIVDVLKPKTPAS GLMSSIGKALGGLIVDVLKPKTPAS

caerin caerin caerin caerin caerin

1.1 1.4 2.2 2.5 3.1

GLLSVLGSVAKHVLPHVVPVIAEHL-NH2 GLLSSLSSVAKHVLPHVVPVIAEHL GLVSSIGRALGGLLADVVKSKEQPA GLVASIGRALGGLLADVVKSKEQPA GLWQKIKDKASELVSGIVEGVK-NH2

L. splendida

345, 407

L. xanthomera

409, 410 caerin 1.6 caerin 1.7

GLFSVLGAVAKHVLPHVVPVIAEK GLFKVLGSVAKHLLPHVAPVIAEK

caerin 1.1 caerin 2.1

GLLSVLGSVAKHVLPHVVPVIAEHL-NH2 GLVSSIGRALGGLLADVVKSKGQPA

caerin 1.1 caerin 1.6 caerin 1.10 caerin 2.1 electrin 2.1

GLLSVLGSVAKHVLPHVVPVIAEHL-NH2 GLFSVLGAVAKHVLPHVVPVIAEKL-NH2 GLLSVLGSVAKHVLPHVVPVIAEKL-NH2 GLVSSIGRALGGLLADVVKSKQPA NEEEKVKWEPDVP-NH2

L. peronii

136, 142

L. rothii

L. electrica

ref

86, 95

138

terminus, have poor antimicrobial activity.392 Removing three residues from the C-terminus of aurein 2.2 does not markedly affect activity against S. aureus and E. coli.393 The antimicrobial activity of aurein 1.2 and citropin 1.1 is enhanced when combined with other antibiotics. For example, synergy is demonstrated when aurein 1.2 is combined with minocycline and clarithromycin.394 Citropin 1.1 shows synergistic effects with polymyxin E, clarithromycin, and tazobactram-piperacillin against surgical wound infections and the oxidative damage of Gram-negative sepsis.395,396 Finally, caerins 3 and 4 inhibit the growth of only a few microbial species tested. However, caerin 3-related peptides from other species of the genus Litoria such as aurein 4.1, dahlein 4.1, and maculatin 3.1 that contain W3 and two or three K residues show no antimicrobial activity. The range of activities of natural L-citropin 1.1 and L-caerin 1.1 highly resemble their D-counterparts. This result shows that L-citropin 1.1 and L-caerin 1.1 do not interact with specific chiral receptors. In fact, most peptides from Litoria frogs have antimicrobial activity because they disrupt membrane integrity and interact with phosphatidylcholine bilayers in the aqueous region of the membrane bilayer.397,398 Fallaxidin 4.1a forms transmembrane pores in bacteria.95 Similarly, caerin 1.1 and maculatin 1.1, which are flexible because of the central P, are transmembrane peptides. Citropin 1.1 and aurein 1.2 are not long enough to span the membrane bilayer but interact with a model membrane by a surface “carpet” mechanism.398−401 Generally, citropin 1.1, caerin 1.1, aurein 1.2, and maculatin 1.1 do not insert deeply into phosphatidylcholine membranes. This is probably why these positively charged peptides have a preference for bacterial over eukaryotic cells.402 In addition, citropin 1.1, aurein 2.2, and aurein 2.3 are proposed to inhibit E. coli, at least in part, by action against ATP synthase.361 2.14.8. Hylarana. More than 80 AMPs have been isolated from H. erythrea, H. guentheri, H. latouchii, H. nigrovittata, H. picturata, and H. temporalis in the Hylarana genus. The AMPs are classified into the families brevinin-1, brevinin-2, temporin,

as caerins 1.1.1 and 1.1.2 consist of the N-terminal residues of caerin 1.1 produced by enzymatic cleavage. Thus, the primary structures of all caerin 1 peptides resemble that of caerin 1.1. The acidic propiece and N-terminal signal portions of the precursors are highly conserved. Preproregions of caerin precursors display distinct similarity to corresponding regions of preprodermaseptin from South American hylid frogs.388 As compared to caerin 1.1 peptides, maculatin 1.1 lacks four residues including P15.389 However, the integrated primary structure of maculatin 1.1 is essential for full activity, and the cationicity of the peptides affects activity because an analog lacking two N-terminal residues loses activity; analogs that are more positive than maculatin 1.1 have strong antibacterial and hemolytic activities.390 Both fallaxidin 4.1 from L. fallax containing three P residues and its corresponding C-terminal amidated peptide, fallaxidin 4.1a, are partially helical. Disruptions in the regions of P7, G11, and G14 produce random coil that can help binding to bacterial membranes.139 AMPs from Litoria frogs have high structural similarity with differences in antimicrobial activity. These differences might be due to differences in length, cationicity, and sequence. As compared to peptides from the aurien, citropin, maculatin families and their analogs, the 16 or 17 residues are an optimal length for Litoria AMPs, and activity decreases with length changes.391 Cationicity also has an important effect on the activity of peptides from Litoria frogs. Increasing cationicity while maintaining the amphipathicity of citropin 1.1 increases its activity against both Gram-negative and Gram-positive microorganisms. Increasing the cationic charge of caerins 1.1 enhances activity toward Gram-negative bacteria but decreases activity toward Gram-positive microorganisms.343 Amidation affects the charge of molecules and thus changes peptide antimicrobial activity. For example, fallaxidin 4.1a has more potent antimicrobial activity toward Gram-positive microorganisms than fallaxidin 4.1, and the caerin 2 peptides, uniquely among caerin molecules lacking an amidated CAG


Chemical Reviews

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Table 18. AMPs from Hylarana and Hyla Frogs source

name

sequence

H. guentheri

ref 412

guentherin temporin-GH brevinin-2GHa brevinin-2GHb brevinin-2GHc

VIDDLKKVAKKVRRELLCKKHHKKLN FLPLLFGAISHLL-NH2 GFSSLFKAGAKYLLKSVGKAGAQQLACKAANNCA GVITDALKGAAKTVAAELLRKAHCKLTNSC SIWEGIKNAGKGFLVSILDKVRCKVAGGCNP

brevinin-1TEa brevinin-2TEa brevinin-2TEb

FFGPLIKIATGVLPNLICKALGKC GIGSMLLGLAKNVGMSLLNKAQCKISGKC GFMGDTLKGIAINAALALMNAAQCKLSGKC

B2RP brevinin-1ERa brevinin-1ERb brevinin-1ERc brevinin-2ERa brevinin-2ERb esculentin-2ERa esculentin-2ERb esculentin-2ERc esculentin-2ERd temporin-ERa

GVIKSVLKGVAKTVALG ML-NH2 FLPGLIKVAAGLIPKVVCKFTNKC FLPTLIKVAANVIPSIICKFTGKC FLPTLIKVAADVIPSIICKFTGKC VVKDTLKSVAKTVALQLVNTAKCKLEKTC GAIKETLKDFAKTVALGLVNTAKCKLEKTC GLFSLFKAGAKILGKTFLKQAGKAGAEHLACKAANQC GILNTLKNVGLGVLKGAGKGALNAVLCKMNNNC GILNTLKNVGLGVLKSAGKGALNAVLCKMNNSC SILTTLKDVGISVAKAAGSGVLKALLCKLNKNCEA FLPLIIGALSSLLPKIF-NH2

brevinin-1LT1 brevinin-1LT2 brevinin-1LTa brevinin-1LTb brevinin-2LTa brevinin-2LTb brevinin-2LTc palustrin-2LTa brevinin-2LT1 brevinin-2LT2 esculentin-2LTa esculentin-2LTb ranacyclin-LTa ranacyclin-LTb esculentin-1LTa esculentin-1LTb temporin-LT1 temporin-LT2 temporin-Lta1 temporin-Lta2 temporin-LTb temporin-LTc temporin-LTe

FMGSALRIAAKVLPAALCQIFKKC FFGSVLKVAAKVLPAALCQIFKKC FFGTALKIAANVLPTAICKILKKC FFGTALKIAANILPTAICKILKKC GAFGDLLKGVAKEAGMKLLNMAQCKLSGKC SILDKIKNVALGVARGAGTGILKALLCKLDKSC GVLDTFKDVAIGVAKGAGTGVLKALLCKLDKSC SLWENFKNAGKQFILNILDKIRCRVAGGCRT GAFGDFLKGAAKKAGLKILSIAQCKLFGTC GAFGDFLKGAAKKAGLKILSIAQCKLSGTC GIFSLFKAGAKFFGKHLLKQAGKAGAEHLACKATNQC SIFSLFKAGAKFFGKNLLKEAGKAGAAHLACKATNQC SALRGCWTKSYPPKPCFGK SALRGCWTKSYPPKPCLGK RISFKKGKGSWIKNGLIKGIKGLGKEISLDVIRTGIDIAGCKIKGEC RISFKKGKGSWIKNGLIKGIKGLGKEIGLDVIRTGIDIAGCKIKGEC FLPGLIAGIAKML-NH2 FLPIALKALGSIFPKIL-NH2 FFPLVLGALGSILPKIFGK-NH2 FFPLVLGALGSILPKIF-NH2 FIITGLVRGLTKLF-NH2 SLSRFLSFLKIVYPPAF-NH2 FLAGLIGGLAKMLGK-NH2

brevinin-2PTa brevinin-2PTb brevinin-2PTc brevinin-2PTd brevinin-2PTe brevinin-1PTa brevinin-1PTb temporin-PTa

GAIKDALKGAAKTVAVELLKKAQCKLEKTC GFKGAFKNVMFGIAKSAGKSALNALACKIDKSC GLLDSFKNAMIGIAKSAGKTALNKIACKIDKTC GFLDSFKNAMIGVAKSAGKTALNTLACKIDKTC GFLDSFKNAMIGVAKSVGKTALSTLACKIDKSC FMGGLIKAATKIVPAAYCAITKKC FMGGLIKAATKALPAAFCAITKKC FFGSVLKLIPKIL-NH2

nigroain-A1 nigroain-A2 nigroain-A3 nigroain-A5 nigroain-A6

SALVGCWTKSYPPKPCF SALVGCGTKSYPPKPCF SALVGCWTKSYPPKPVSVDDKTCLANHLMWNIIWLNARCLMKK SALVGCWTKSYPPKPCI SALVGCWTKSYPPNPCF

H. temporalis

416

H. erythraea

411

H. latouchii

413, 414

H. picturata

415

H. nigrovittata

4, 196

AH


Chemical Reviews

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H. punctata H. biobeba

name

sequence

nigroain-A7 nigroain-A8 nigroain-B1 nigroain-B2 nigroain-B3 nigroain-B4 nigroain-B5 nigroain-C1 nigroain-C2 nigroain-D1 nigroain-D2 nigroain-D3 nigroain-E1 nigroain-E2 nigroain-I1 nigroain-G1 nigroain-H1 nigroain-H2 nigroain-K1 nigroain-K2 nigroain-L1 gaegurin-RN1 gaegurin-RN2 gaegurin-RN3 gaegurin-RN4 gaegurin-RN5 gaegurin-RN6 gaegurin-RN7 rugosin-RN1 rugosin-RN2 rugosin-RN3 rugosin-RN4 rugosin-RN5 rugosin-RN7 rugosin-RN6 rugosin-RN8 rugosin-RN9 temporin-RN1 temporin-RN2 temporin-RN3 ranacyclin-B-RN1 ranacyclin-B-RN2 brevinin-2-RN1 brevinin-2-RN2 hylaseptin P1

SALVGCWTKS SALVGCWTKSYPP CVISAGWNHKIRCKLTGNC CVISAGWDHKVRCKLTGNC CKI-ALPYH-MRCRVLGRC CVISAGWNHKIR CKIALPYT FKTWKRPPFQTSCSGIIKE FKTWKRPPFQTSCWGIIKE CVHWQTNPARTSCIGP CVHWQTNPARTSRIGP CVHWQTNTARTSCIGP DCTRWIIGINGRICRD GCTQWINNIHGRICVRN SFLSKFKDIALDVPRMRARVY CTCRVLDQELSTKALFR DLQRRCKIALPYHMRCRVLGRC DLQRRCKIALPYT SLWETIKNAGKGFIQNILDKIR SLWETIKNAGKGFILNILDKIRCKVAGGCKT PPMGYLH FIGPVLKIAAGILPTAICKIFKKC FIGPVLKIATSILPTAICKIFKKC FLGPIIKIATGILPTAICKILKKC FVGPVLKIAAGILPTAICKIYKKC FLGPIIKIATGILPTAICKFLKKC FLGPIIKIATGILPTAICKILKKMLKLWKWKSSDVEYHLAKCTSDVL FLGPIIKIATGILPTAICKILKNVETLEMEII SIRDKIKTIAIDLAKSAGTGVLKTLICKLDKSC SIRDKIKTIAIDLAKGAGTGVLKTLICKLDKSC SIRDKIKTIAIDLAKSAGMGILKTLICKLDKSC SIRDKIKTIAIDLAKSAGTGVLKTSICKLDKSC SIRDKIKTIAIDLAKSAGTGVLKTLICKLNKSC RFLSKFKDIALDVAKNAGKGVLTTLACKIDGSC SFLSKFKDIALDVAKNAGKGVLTTLACKIDGSC SFLSKFKDIALDVAKNAGKGVLTTLARKIDGSC SFLSKIKDIALDVAKNAGKGVLTTLACKIDGSC FLPLVLGALSGILPKIL-NH2 FFPLLFGALSSLLPKLF-NH2 FFPLLFGALSSHLPKLF-NH2 SALVGCWTKSYPPLPCFGR SALVGCGTKSYPPLPCFGR GAFGNFLKGVAKKAGLKILSIAQCKLSGTC GAFGNFLKGVAKKAGLKILSIAQCKLFGTC GILDAIKAIAKAAG

hylin-b1 hylin-b2

FIGAILPAIAGLVHGLINR-NH2 FIGAILPAIAGLVGGLINR-NH2

hylain 1 hylain 2

GILDAIKAFANALG-NH2 GILDPIKAFAKAAG-NH2

He-1 He-2

DDDKTEEEDDKENETTKVVE ADYRCELSRNYGKGSSSFTYYYYDKATSI

H. simplex

ref

418 419

33

H. eximia

420

random coil in water. These peptides also contain a heptapeptide ring known as a rana box formed by a disulfide bond at the C-terminus.417 In contrast to the brevinin peptides identified from the above six species, esculentin-2 peptides from Hylarana have been

esculentin-1, esculentin-2, guentherin, and ranacyclin (Table 18).196,411−416 Brevinin-2 peptides have conserved K7, C27, K28, C33 residues, and brevinin-1 peptides have conserved A9, C18, K23, C24 residues.350 Brevinin-1 peptides adopt an extended αhelical conformation in a membrane-mimetic solvent and a AI


Chemical Reviews

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Table 19. AMPs from Pseudis, Hypsiboas, Agalychnis, Hylomantis, and Pachymedusa Frogs source

name

sequence

P. paradoxa pseudin-1 pseudin-2 pseudin-3 pseudin-4

GLNTLKKVFQGLHEAIKLINNHVQ GLNALKKVFQGIHEAIKLINNHVQ GINTLKKVIQGLHEVIKLVSNHE GINTLKKVIQGLHEVIKLVSNHA

hylaseptin-P1 phenylseptin

GILDAIKAIAKAAG FFFDTLKNLAGKVIGALT-NH2

raniseptin-1 raniseptin-2 raniseptin-3 raniseptin-4 raniseptin-5 raniseptin-6 raniseptin-7 raniseptin-8 raniseptin-9

AWLDKLKSLGKVVGKVALGVAQNYLNPQQ AWLDKLKSLGKVVGKVAIGVAQHYLNPQQ AWLDKLKSIGKVVGKVAIGVAKNLLNPQ AWLDKLKSLGKVVGKVGLGVVQNYLNPRQ AWLDKLKNLGKVVGKVALGVVQNYLNPRQ ALLDKLKSLGKVVGKVALGVVQNYLNPRQ ALLDKLKSLGKVVGKVALGVAQHYLNPQQ ALLDKLKSLGKVVGKVAIGVAQHYLNPQQ ALLDKLKSLGKVVGKVAIGVAQHYLNPQ

hylin-a1 Ctx-Ha

IFGAILPLALGALKNLIK-NH2 GWLDVAKKIGKAAFNVAKNFL-NH2

H. punctatus

418, 427

H. raniceps

424

H. albopunctatus

425, 426

A. annae

388, 432 dermaseptin dermaseptin dermaseptin dermaseptin dermaseptin dermaseptin

AA-1-1 AA-2-5/plasticin-A1 AA-3-1 AA-3-3 AA-3-4 AA-3-6

SLGSFMKGVGKGLATVGKIVADQFGKLLEA GLVSGLLNTAGGLLGDLLGSLGSLSG-NH2 SLWSKIKEMAATAGKAALNAVTGMVNQ-NH2 GMFTNMLKGIGKLAGQAALGAVKTLA-NH2 GMWGSLLKGVATVVKHVLPHALSSQQS GMWSTIRNVGKSAAKAANLPAKAALGAISEAV-NH2

A. callidryas

A. litodryas H. lemur

ref 421

388, 428, 430 DRP-AC1 DRP-AC2 DRP-AC3 ARP-AC1 CRP-AC1 DRP-AC4 medusin AC plasticin-C1 plasticin-C2 dermaseptin-LI1

GLLSGILNTAGGLLGNLIGSLSNGES-NH2 GLLSGILNSAGGLLGNLIGSLSNGES-NH2 SVLSTITDMAKAAGRAALNAITGLVNQGEQ-NH2 GMWSKIKEAGKAAAKAAAKAAGKAALDVVSGAI-NH2 GMWGTVFKGIKTVAKHLLPHVFSSQQS SLLSTLGNMAKAAGRAALNAITGLVNQ-NH2 LLGMIPLAISAISALSKLG-NH2 GLLSGILNTAGGLLGNLIGSLSN-NH2 GLLSGILNSAGGLLGNLIGSLSN-NH2 AVWKDFLKNIGKAAGKAVLNSVTDMVNE

phylloseptin-L1 dermaseptin-L1

LLGMIPLAISAISALSKL-NH2 GLWSKIKEAAKAAGKAALNAVTGLVNQGDQPS

dermaseptin PD-1-5 dermaseptin PD-2-2 dermaseptin PD-3-3 dermaseptin PD-3-6/plasticin-DA1 dermaseptin PD-3-7 dermaseptin DRG1 dermaseptin DRG2 dermaseptin DRG3 medusin PD

SLGSFMKGVGKGLATVGKIVADQFGKLLEAGKG ALWKTLLKKVGKVAGKAVLNAVTNMANQNEQ GMWSKIKNAGKAAAKASKKAAGKAALGAVSEAL-NH2 GVVTDLLNTAGGLLGNLVGSLSG-NH2 LLGDLLGQTSKLVNDLTDTVGSIV GLWSNIKTAGKEAAKAALKAAGKAALGAVTDAV-NH2 GLWSKIKEAGKAVLTAAGKAALGAVSDAV-NH2 ALWKTIIKGAGKMIGSLAKNLLGSQAQPES LLGMIPLAISAISSLSKLG-NH2

P. dacnicolor

289 429

430−432

reported only from H. erythrea and H. temporalis. Like the brevinin-1 peptides, esculentin-2 peptides also contain a heptapeptide ring and conserved residues G1, K19, C31, K32, and C37.417 Esculentin-1LTa and esculentin-1LTb from H. latouchii are the only peptides from Hylarana frogs in the esculentin-1 family. However, esculentin-1LTa and esculentin-1LTb contain

47 aa and are one residue longer than other esculentin-1 peptides. Furthermore, their N-termini start with R rather than the G that appears at the N-terminus of most esculentin-1 peptides. Additionally, esculentins-1LTs have high peptide cationicity and low hydrophobicity, which promote interaction with the negatively charged bacterial cell membrane and reduce AJ


Chemical Reviews

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Table 20. AMPs from Phyllomedusa Frogs source

name

sequence

P. hypochondrialis

ref 430, 451, 462−465

dermaseptin H1 dermaseptin-H2 dermaseptin H3 dermaseptin H5 dermaseptin H7 dermaseptin-1/dermaseptin H4 dermaseptin-2 dermaseptin-3 dermaseptin-4 dermaseptin-5/dermaseptin H6 dermaseptin-6 dermaseptin-7 hyposin-1 hyposin-2 hyposin-3 hyposin-4 hyposin-5 phylloseptin-1 phylloseptin-2 phylloseptin-3 phylloseptin-4 phylloseptin-5 phylloseptin-6 phylloseptin-7 phylloseptin-8 phylloseptin-9 phylloseptin-10 phylloseptin-11 phylloseptin-12 phylloseptin-13 phylloseptin-14 phylloseptin-15 medusin PH distinctin-like peptide

GLWKSLLKNVGVAAGKAALNAVTDMVNQ-NH2 ALWKSLLKNVGVAAGKAALNAVTDMVNQ-NH2 GLWSTIKNVAAAAGKAALGAL-NH2 GLWSTIKNVGKEAAIAAGKAVLGSL-NH2 GLWSKIKDVAAAAGKAALGAVNEAL-NH2 GLWSTIKNVGKEAAIAAGKAALGAL-NH2 GLWKSLLKNVGVAAGKAALNAVTDMVNQ ALWKDVLKKIGTVALHAGKAAFGAAADTISQGGS GLWSTIKQKGKEAAIAAAKAAGKAVLNAASEAL-NH2 GLWSTIKQKGKEAAIAAAKAAGQAALGAL-NH2 GLWSTIKQKGKEAAIAAAKAAGQAVLNSASEAL-NH2 GLWSTIKQKGKEAAIAAAKAAGQAVLNAASEAL-NH2 LRPAVIRPKGK-NH2 LRPAFIRPKGK-NH2 LRPAVIVRTKGK-NH2 FRPALIVRTKGTRL-NH2 LGPALITRKPLKGKP FLSLIPHAINAVSAIAKHN-NH2 FLSLIPHAINAVSTLVHHF-NH2 FLSLIPHAINAVSALANHG-NH2 FLSLIPHAINAVSTLVHHSG-NH2 FLSLIPHAINAVSAIAKHS-NH2 SLIPHAINAVSAIAKHF-NH2 FLSLIPHAINAVSAIAKHF-NH2 FLSLIPTAINAVSALAKHFG-NH2 FLGLLPSIVSGAVSLVKKL-NH2 FLSLLPSLVSGAVSLVKKL-NH2 FLSLLPSLVSGAVSLVKIL-NH2 FLSLLPSIVSGAVSLAKKL-NH2 FLSLIPHAINAVGVHAKHF-NH2 FLSLIPAAISAVSALADHF-NH2 LLSLVPHAINAVSAIAKHF-NH2 LLGMIPVAISAISALSKLG-NH2 NLVSALIEGRKYLKNVLKKLNRLKEKNKAKNSKENN

phylloseptin-H1

FLSLIPHAINAVSAIAKHN-NH2

dermaseptin-B1 dermaseptin-B2/adenoregulin dermaseptin-B3 dermaseptin-B4 dermaseptin-B5 dermaseptin-B6 dermatoxin B1 PBN1/phyllosepptin-B1 PBN2/plasticin-B1 phylloseptin-B2 phylloxin B1 SPYY

AMWKDVLKKIGTVALHAGKAALGAVADTISQ-NH2 GLWSKIKEVGKEAAKAAAKAAGKAALGAVSEAV-NH2 ALWKNMLKGIGKLAGQAALGAVKTLVGAE ALWKDILKNVGKAAGKAVLNTVTDMVNQ-NH2 GLWNKIKEAASKAAGKAALGFVNEMV-NH2 ALWKDILKNAGKAALNEINQLVNQ-NH2 SLGSFLKGVGTTLASVGKVVSDQFGKLLQAGQ-NH2 FLSLIPHIVSGVAALAKHL-NH2 GLVTSLIKGAGKLLGGLFGSVTGGQS FLSLIPHIVSGVASIAKHF-NH2 GWMSKIASGIGTFLSGMQQG YPPKPESPGEDASPEEMNKYLTALRHYINLVTRQRY-NH2

DRS-DI4-like peptide DS VIII-like peptide dermaseptin III-like peptide distinctin A chain distinctin B chain

ALWKNMLKGIGKLAGQAALGAVKTLVGA ALWKTMLKKLGTVALHAGKAALGAAADTISQGA ALWKNMLKGIGKLAGKAALGAVK ENREVPAGFTALIKTLRKCKII NLVSGLIEARKYLEQLHRKLKNCKV

dermadistinctin-K dermadistinctin-L dermadistinctin-M distinctin A chain

GLWSKIKAAGKEAAKAAAKAAGKAALNAVSEAV ALWKTLLKNVGKAAGKAALNAVTDMVNQ ALWKTMLKKLGTMALHAGKAAFGAAADTISQ ENREVPPGFTALIKTLRKCKII

P. azurea

453

P. bicolor

388, 440, 458, 466−469

P. burmeisteri

442, 468, 470

P. distincta

471, 472

AK


Chemical Reviews

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name

sequence

distinctin B chain dermadistinctin-Q1 dermadistinctin-Q2

NLVSGLIEARKYLEQLHRKLKNCKV ALWKNMLKGIGKLAGQAALGAVKTLVGAES GLWSKIKEAAKTAGLMAMGFVNDMV

dermaseptin-S1 dermaseptin-S2 dermaseptin-S3 dermaseptin-S4 dermaseptin-S5 phylloseptin-S1 phylloseptin-S2 phylloseptin-S3 phylloseptin-S4 phylloseptin-S5 phylloseptin-S6

ALWKTMLKKLGTMALHAGKAALGAAADTISQGTQ ALWFTMLKKLGTMALHAGKAALGAAANTISQGTQ ALWKNMLKGIGKLAGKAALGAVKKLVGAES ALWMTLLKKVLKAAAKALNAVLVGANA GLWSKIKTAGKSVAKAAAKAAVKAVTNAV FLSLIPHIVSGVASIAKHF-NH2 FLSLIPHIVSGVASLAKHF-NH2 FLSLIPHIVSGVASLAIHF-NH2 FLSMIPHIVSGVAALAKHL-NH2 LLGMIPVAISAISALSKL-NH2 FLSLIPHIVSGVASIAKHL-NH2

dermaseptin-S6 dermaseptin-S7 dermaseptin-S8 dermaseptin-S9 dermaseptin-S10/Plasticin-S1 dermaseptin-S11 dermaseptin-S12 dermaseptin-S13 dermatoxin S phylloxin-S1/PLX-S PSN-1

GLWSKIKTAKEAAKAAAKAAGKAALNAVSEAI-NH2 GLWKSLLKNVGEAAGKAALNAVTDMVNQ-NH2 ALWKTMLKKLGTVALHAGKAALGAAADTISQ-NH2 GLRSKIWLWVLLMIWQESNKFKKM GLVSDLLSTVTGLLGNLGGGGLKKI ALWKTLLKGAGKVFGHVAKQFLGSQGQPES GLWSKIKEAAKTAGKMAMGFVNDMV-NH2 GLRSKIKEAAKTAGKMALGFVNDMA-NH2 ALGTLLKGVGSAVATVGKMVADQFGKLLQAGQ-NH2 GWMSKIASGIGTFLSGVQQ-NH2 FLSLIPHIVSGVASIAKHF-NH2

dermaseptin-1 dermaseptin-2 dermaseptin-3 dermaseptin-4 dermaseptin-5 dermaseptin-6 dermaseptin-7/DRS LIKE dermaseptin-8 phylloseptin-1 phylloseptin-2 phylloseptin-3

GLWSKIKETGKEAAKAAGKAALNKIAEAV ALWKDILKNVGKAAGKAVLNTVTDMVNQ GLFKTLIKGAGKMLGHVAKQFLGSQGQPES ALWKDILKNAGKAALNEINQIVQ GLWSKIKEAAKTAGKAAMGFVNEMV ALWKNMLKGIGKLAGQAALGAVKTLVGA ALWKDVLKKIGTVALHAGKAALGAVADTISQ SLRGFLKGVGTALAGVGKVVADQFDKLLQAGQ FLSLIPKIAGGIASLVKNL FLSLIPHIATGIAALAKHL FFSMIPKIATGIASLVKNL

dermaseptin-01 phylloseptin 4 phylloseptin 5 phylloseptin 6 phylloseptin 7 phylloseptin 8

GLWSTIKQKGKEAAIAAAKAAGQAALGAL-NH2 FLSLIPHAINAVSTLVHHSG-NH2 FLSLIPHAINAVSAIAKHS-NH2 SLIPHAINAVSAIAKHF-NH2 FLSLIPHAINAVSAIAKHF-NH2 FLSLLPTAINAVSALAKHF

DRS-H9 DRS-01/DRS-H7 DRS-H15 DRS-H3/DRS-H12 DRS-H10 PLS-H5 PLS-H6 PLS-S1 HPS-H2 HPS-J1 PLS-H8b PLS-H8

GLWSTIKQKGKEAAIAAAKAAGQAALNAASEAL-NH2 GLWSTIKQKGKEAAIAAAKAAGQAALGAL-NH2 GLWSKIKDVAAAAGKAALGAVNEAL-NH2 GLWSTIKNVGKEAAIAAGKAALGAL-NH2 GLWSTIKNVAAAAGKAALGAL-NH2 FLSLIPHAINAVSAIAKHF-NH2 FLSLIPTAINAVSALAKHF-NH2 LLGMIPVAISAISALSKL-NH2 LRPAFIRPKGK-NH2 FRPALIVRTKGK-NH2 FLSLLPSLVSGAVSLVKK FLSLLPSLVSGAVSLVKKL

P. sauvagii

ref

455

P. sauvagei

435, 441, 454, 467, 473

P. tarsius

474, 475

P. oreades

451, 462, 465, 476

P. nordestina

477

AL


Chemical Reviews

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against Candida species. Structural studies show that hylin a1 has an amphipathic α-helix conformation with hydrophobic and hydrophilic residues on opposite sides of a high helix content.425 An analog of hylin a1 containing W instead of L6 has MIC values comparable to those of the original peptide. Two peptides containing an extra acetyl group or D residue at the N-terminus in addition to a W6 substitution display activity only against Gram-positive bacteria, indicating that the Nterminal region of hylin a1 is important for antibacterial activities against different types of bacteria. Another peptide from the skin secretions of the frog H. albopunctatus, Ctx-Ha, has sequence similarity to ceratotoxin. An analog, Ctx (Ile21)Ha, has a high amount of α-helical conformation in the presence of trifluoroethanol and lysophosphatidylcholine, which kills microbes based on a barrel-stave model. Destruction of the amphipathic α-helix of Ctx (Ile21)-Ha by replacement of I with K is less harmful to the structure than D-aa substitutions.426 Phenylseptins are purified from H. punctatus in two naturally occurring D-Phe and L-Phe configurations. Both peptides exhibit distinct activity against pathogenic S. aureus, E. coli, and Pseudomonas aeruginosa. The D-Phe configuration is more effective than the L-Phe. This difference can be explained by structural divergences that show a major 90° difference between the two backbones at the first four residues from their N-termini and substantial alterations in the orientation of side chains.427 2.14.12. Agalychnis, Hylomantis, and Pachymedusa. Although many AMPs have been reported from the Central and South American tree frogs classified in the genera Phyllomedusa, Agalychnis, Hylomantis, and Pachymedusa, only few peptides from species in the last three genera are reported to have antimicrobial activities (Table 19). ARP-AC1 and DRPAC4 from the red-eyed leaf frog A. callidryas exhibit antimicrobial activities against E. coli and Micrococcus luteus, while CRP-AC1 from the same species has effects only against M. luteus.428 Dermaseptin-L1 and phylloseptin-L1 from H. lemur inhibit the growth of Batrachochytrium dendrobatidis zoospores and possess cytolytic activity. However, dermaseptinL1 is active against E. coli but inactive against S. aureus, while phylloseptin-L1 is active against S. aureus but inactive against E. coli.429 Two peptides in the medusin family from A. callidryas and P. dacnicolor are C-terminally amidated and have the highly conserved sequence LGMIPL/VAISAISA/SLSKL-NH2. All exhibit activities against S. aureus and C. albicans but no hemolytic effects at concentrations effective against both microorganisms.430 Four GL-rich dermaseptin-related peptides in the plasticin family are plasticin-C1 and plasticin-C2 from A. callidryas, plasticin-A1 from A. annae, and plasticin-DA1 from P. dacnicolor, which are weakly cationic or neutral and show no antimicrobial activities.388,431,432 2.14.13. Phyllomedusa. Species in the subfamily Phyllomedusinae are a rich source of AMPs, predominantly from Phyllomedusa.433 On the basis of primary structural similarities and activities, these peptides are divided into distinct families or subfamilies of dermaseptin, dermatoxin, distinctin, phylloseptin, phylloxin, plasticin, and SPYY (Table 20).431,433,434 Dermaseptins, a large family of AMPs identified from Phyllomedusa frog skins, are a large class of K-rich polycationic peptides with two apparent separated lobes of negative and positive electrostatic surface, leading to a transition from coil to helix after binding to lipid bilayers. 434 Although the dermaseptins differ both in length and in aa sequence, they

hemolysis. This feature explains their wide-ranging antimicrobial activities with high potency but low hemolyticity.413,414 All temporins from the Hylarana genus are acyclic and highly variable and have C-terminal amidation. Like most temporin AMPs, temporins from Hylarana frogs have antimicrobial effects only on Gram-positive bacteria and different hemolytic activity. Guentherin from H. guentheri does not show sequence similarity with any known AMPs despite its distinct antimicrobial activity against S. aureus.413,414 Like esculentin1LTa, guentherin is highly positively charged with 3 acidic and 12 basic residues that are related to its potent antimicrobial activity.402 Ranacyclin-B-RN1 and ranacyclin-B-RN2 from H. nigrovittata show strong antimicrobial activity against S. aureus (MIC = 6 and 12.7 μM, respectively) and trypsin-inhibitory abilities with Ki around 10−6 M.196 2.14.9. Hyla. Although the Hyla genus has 33 species, only 7 AMPs have been identified from H. biobeba, H. simplex, H. eximia, and H. punctata. Those AMPs are shorter than 20 residues. All are linear, cationic α-helical peptides and inhibit the growth of a wide range of microorganisms.33,418−420 In contrast from other Hyla AMPs, hylins b1 and b2 from the skin secretions of the Brazilian Hylidae frog H. biobeba contain a large number of hydrophobic residues and an amidated Cterminus, and have hemolyticity.419 In addition, hylaseptin P1 from H. punctata kills pathogens through direct interaction with the cell membrane, leading to a progressive process of permeabilization and cell lysis.418 2.14.10. Pseudis. The South American frog P. paradoxa is the only Pseudis species from which AMPs have been identified (Table 19). Pseudins 1−4 identified from this species are structurally related, cationic, amphipathic α-helical AMPs with a wide range of antimicrobial activities. One AMP, the lowhemolytic pseudin-2, has the most potent activities against broad-spectrum microorganisms, particularly Gram-negative bacteria.421 Analogs of pseudin-2 with up to three K replacements show progressive potency against broad-spectrum Gram-positive and Gram-negative bacteria while maintaining low hemolyticity. However, when the number of K residues is increased to 4 or 5, only hemolytic activity toward human erythrocytes increases. Different from most AMPs, substitution of neutral aa on the hydrophobic face of the α-helix with F, which increases hydrophobicity while maintaining the amphipathicity of pseudin-2, has no major effects on antimicrobial or hemolytic activities.422 Pseudins have sequence identity with the partial C-terminal region of DEFT, a death effector domaincontaining protein expressed in mammalian testicular germ cells and involved in regulating apoptosis. Pseudin-2 forms pores in bacterial membranes to collapse the membrane potential, release intracellular materials, and inhibit macromolecule synthesis through binding to RNA. These features explain its potent antimicrobial activity against a wide range of microorganisms.423 2.14.11. Hypsiboas. AMPs have been identified from several Hypsiboas frogs including H. raniceps, H. albopunctatus, and H. punctatus (Table 19). Raniseptin AMPs have been identified in skin secretions of H. raniceps. These AMPs share some structural similarity with dermaseptins and antimicrobial activities against different bacterial strains without significant hemolytic activity.424 Hylin a1 from H. albopunctatus exhibits a more prominent effect against Gram-positive bacteria with strong hemolytic activities. Hylin a1 also exhibits activity AM


Chemical Reviews

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generally contain a W3 residue and a conserved motif (AAXKAALXA, where X is any aa) in the center or Cterminus, while dermaseptin-S9 from the skin secretions of P. sauvagei lacks these conserved structural characteristics.435 Dermaseptins and their analogs have lytic activity in vitro and antimicrobial ability with different efficiency and cytolytic activities against a wide range of free-living microorganisms.433,434 In particular, dermaseptin-S1, dermaseptin-S3, dermaseptin-S4, and dermaseptin-S5 from P. sauvagii have relatively high potency, broad-spectrum inhibition of Gramnegative and Gram-positive bacteria, and different cytolytic activities. Dermaseptin-S1, dermaseptin-S3, and dermaseptin-S5 display only weakly hemolytic activities, while dermaseptin-S4 has potent hemolytic and spermicidal activities.436 Truncation analysis of dermaseptin-S3 found that the 1−16 fragment has full antimicrobial potency.437 In addition, when dermaseptins are combined with other antibiotic molecules or AMPs, their antimicrobial potency increases 100-fold.438,439 Dermatoxin S from P. sauvagei and dermatoxin B1 from P. bicolor in the dermatoxin family lack the W residue in their primary structure and have instead a G3 residue and common LLQAGQ sequence at the C-terminus.440,441 Antimicrobial activities of dermatoxin B1 are based on changes in plasma membrane permeability rather than peritrophic membrane solubilization and might be associated with ion channels through the peritrophic membrane.440 Like dermaseptins, dermatoxin B1 inhibits the growth of wall-less Gram-positive and Gram-negative bacteria. Distinctins from P. burmeisteri and P. distincta show potent antimicrobial activity against Gram-negative and Gram-positive bacteria and have 22-residue A and 25-residue B chains linked covalently by a disulfide bond between C19 from the A chain and C23 from the B chain. The cDNA sequences separately encoding chains A and B of heterodimeric distinctins have been found in both species. The A chains have one amino acid difference while the B chains are identical. Although a monomer of predicted products has not been detected in skin secretions, one of two possible homodimers has been detected at low concentrations.442 Homodimeric peptides in water show a fold with a symmetrical full-parallel four-helix bundle that includes a secluded hydrophobic core and exposed basic residues. This structural feature protects distinctin from proteases while maintaining its membrane interaction properties.443 Heterodimeric distinctin in the presence of a lipid membrane contains a long helix that is somewhat parallel to the lipid bilayer and a short helix that forms a ∼24° angle to the bilayer plane. Membrane interactions result in considerable conformational rearrangements of the heterodimer and formation of a voltage-dependent ion channel in the lipid bilayer.444−446 Distinctin and its monomeric analogs have comparable antimicrobial activities. In murine models, this peptide alone or combined with other antibiotics successfully treats topical infections and severe Staphylococcal infections.447,448 Distinctin increases the potency of betalactams and glycopeptides against Staphylococcal biofilms in an experimental model of central venous catheter infections.438 Phylloxin B1 from P. bicolor and phylloxin S1 from P. sauvagei belong to a preprodermorphin/dermaseptins-derived peptide family and have considerable identity at the N-termini of their precursors.441,449 Furthermore, although preprophylloxin and preprodermorphin share homology, their mature peptides are not similar.449,450 Structural studies show that phylloxin B1 has 60−70% α-helical conformation and is

predicted to contain an amphipathic helix spanning residues 1−19.449 Phylloxin B1 inhibits wall-less S. aureus and P. aeruginosa and is ineffective against S. typhimurium.449 In addition, phylloxin B1 appears to have stronger antimicrobial activity against Gram-positive bacteria than Gram-negative bacteria. Phylloseptins from skin secretions of Phyllomedusa frogs are K/H-rich AMPs. Most contain 19−20 residues including 1−3 H residues. Phylloseptins also generally have a highly conserved sequence FLSLI[L]P at the N-terminus and a variable amidated C-terminal region.451 In a membrane-mimetic environment, phylloseptins adopt α-helical amphipathic conformations stabilized by electrostatic interactions of the two ends of the helix as well as other contributions such as hydrophobic and capping interactions.452 This structure promotes binding with and insertion into a membrane characterized by many bubblelike formations and membrane collapse at a threshold concentration.451 Although only a few of these peptides have had their antimicrobial activity fully tested, phylloseptins exhibit potent antimicrobial effects against broad-spectrum Gramnegative and Gram-positive bacteria and weak effects on fungal growth.451 These peptides exhibit negligible or no hemolytic activity and some cytotoxic effects only at high concentrations.451,453 Thus, these peptides appear to be somewhat selective for bacterial rather than fungal membranes.451,452 Like dermaseptins, phylloseptins often have multiple homologues in a given species with high identity in aa sequence. However, the antimicrobial activities and target microorganism specificities of orthologous and paralogous peptides are clearly different. For example, phylloseptins 1−3 from P. hypochondrialis show 74% sequence similarity and almost identical ability to inhibit Grampositive and Gram-negative bacteria.451,452 Phylloseptin-S1, phylloseptin-S2, and phylloseptin-S4 from P. sauvagii share 79−95% aa sequence identity and two positive charges and strongly inhibit Gram-positive bacteria. Although phylloseptinS3 has 95% aa similarity with phylloseptin-S2 and phylloseptinS5 from the same species and two positive charges, it is almost inactive against bacteria. Phylloseptin-1 and phylloseptin-S1 have 63% aa sequence identity but are 10-fold different in MIC against E. coli.451,454,455 According to structural studies, these significantly different potencies against microorganisms are due to divergence in α-helical folding propensity and/or degree of amphipathicity.455 Like plastictins from Agalychni and Pachymedusa frogs, plasticin-B1 from P. bicolor and plasticin-S1 from P. sauvagei are also GL-rich dermaseptin-related peptides in the plasticin family.388,431,432,454,456 In contrast, plasticin-B1 and plasticin-S1 are strongly cationic, contain K residues, and display potent broad spectrum antimicrobial activity and hemolytic activity.457 All six plasticins are similar in aa sequence, amphipathicity, and hydrophobicity but differ substantially in net charge and conformational plasticity.431 In addition, they contain multiple GXXXG motifs (where X is any aa), which are important for self-association of plasticins and reported to mediate interactions between transmembranes and peptide helixes.434,458 Plasticins show greater conformational flexibility than amphipathic helical dermaseptins because plasticins can adopt helices, destabilized helices, β-sheets, β-hairpins, and disordered states in membrane-mimetic environments.456,457,459 The structural features of plasticins allow them to bind and disrupt the membranes of cells and modulate intracellular targets, leading to various functions. Like some peptides from Phyllomedusa frogs, a region of cationic plasticins with a turn can sometimes AN


Chemical Reviews

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fold into β-hairpin-like structures. This process is determined by the residue at position 8, which is important in inducing the structural change.457,458 Although conformational stability generally does not greatly affect antimicrobial ability, plasticins with different conformations show different antimicrobial abilities. An α-helical structure decreases antimicrobial abilities and results in subtle differences in the antimicrobial potencies of the most active plasticins. This structure is prevented in solution after a β-hairpin is formed that acts as a conformational lock.457 The distribution of charges along plasticins and their structural interconversion properties at the membrane interface are responsible for their distinct interfacial behaviors.460 Reduction of the positive net charge of plasticin-B1 reduces its antimicrobial activity.458 SPYY from P. bicolor frog skin belongs to the NPY family. In addition to melanotropin-releasing activity, SPYY has broadspectrum inhibition of Gram-negative bacteria, Gram-positive bacteria, and fungi.461 2.14.14. Uperoleia. Uperins are structurally related peptides isolated from the Australian frogs U. inundata and U. mjoberii; they have antimicrobial activities against a wide spectrum of bacteria (Table 21).124,478 Uperins have 17−19 aa

mised patients when combined with clarithromycin and doxycycline.480 2.14.15. Crinia. Ten AMPs in four different families have been identified from three Cinia species, C. deserticola, C. riparia, and C. signifera (Table 21). Signiferin 1 has 10 residues, most of which are in a disulfide-bridged octapeptide segment in the C-terminus. Signiferin might be the smallest AMP. The sequences of both signiferin 2.1 and 2.2 from C. signifera start with I and differ by a single residue. Both inhibit the growth of Gram-positive bacteria.253 Furthermore, the I1 residue at Nterminus is not essential for activity because a G-substituted version and the original signiferin 2.1 have a similar spectrum of antimicrobial activity. Signiferin belongs to the same peptide family as riparian-2.1 from C. riparia.254 Deserticolin-1 from C. deserticola is the same family with signiferin-4 from C. signifera. Signiferin-3 also shows significant structural similarity to signiferin-4. 2.14.16. Xenopus. More than 60 AMPs have been identified from skin secretions of Xenopus amphibians including X. amieti, X. andrei, X. borealis, X. clivii, X. lenduensis, X. muelleri, X. petersii, X. pygmaeus, and the F1 hybrids of X. laevis and X. muelleri (Table 22).104,105,481−486 These AMPs belong to the families magainin, CPF, peptide glycine-leucine amide (PGLa), and xenopsin-precursor fragment (XPF) and have distinct structural identities at the N-termini of their precursors, indicating that they might derive from a common ancestral gene through a series of duplication events. On the basis of nucleotide sequence analysis of cloned cDNAs from X. laevis skin, preprocaerulein originates at least in part from different genes rather than alternative splicing of pre-mRNAs to produce caerulein and CPF peptides.104,487 The sequences of CPF and XPF peptides are highly variable, while members of the PGLa family are the most strongly conserved followed by members of the magainin family. Nevertheless, both the XPF and the CPF peptides have conservative amphipathic α-helical structures.485,488 In addition, none of these peptides have C residue or disulfide bridges. Xenopus antimicrobial peptides differ in their antimicrobial and hemolytic activities. The amphipathic, cationic, α-helical magainins have modest antimicrobial activities against both Gram-negative and Gram-positive microorganisms and penetrate bacterial membrane bilayers. Although magainin II inhibits only Gram-positive bacteria with very low potency, its Ksubstitution, pexiganan, exhibits a wide range of potent antimicrobial activities and low toxicity against mammalian cells.488 CPF peptides generally have more potent antimicrobial activity than maginin family members. CPF-AM1, CPF-AM4, and PGLa-AM1 from X. amieti, CPF-B1 from X. borealis, CPFC1 from X. clivii, and CPF-PG1 from X. pygmaeus show high antimicrobial potency against a range of microbes including clinical pathogens and antibiotic-resistant bacteria.105,106,481,484 Thus, they have the potential for development into antiinfective agents. However, some AMP genes appear nonfunctional, and the synthetic corresponding peptides lack antimicrobial activity. For example, neither the peptides magainin-AM1 nor PGLa-AM2 inhibit E. coli and S. aureus growth at high concentrations.481 2.14.17. Silurana. The PGLa, CPF, and XPF AMPs from Xenopus amphibians are also reported in S. tropicalis, S. paratropicalis, and S. epitropicalis with various multiplicities, while magainins are not detected in Silurana skin secretions despite the appearance of relevant genes in their genomes (Table 22). This suggests that nonfunctionalization has been

Table 21. AMPs from Uperoleia and Crinia Frogs source

name

sequence

U. inundata uperin-2.1 uperin-2.2 uperin-2.3 uperin-2.4 uperin-2.5 uperin-3.1 uperin-4.1

GIVDFAKKVVGGIRNALGI GFVDLAKKVVGGIRNALGI GFFDLAKKVVGGIRNALGI-NH2 GILDFAKTVVGGIRNALGI GIVDFAKGVLGKIKNVLGI-NH2 GVLDAFRKIATVVKNVV-NH2 GVGSFIHKVVSAIKNVA-NH2

uperin-3.5 uperin-3.4 uperin-3.7 uperin-3.6 uperin-2.8 uperin-2.7 uperin-2.6

GVGDLIRKAVSVIKNIV-NH2 GVGDLLRKAVAALKNLV-NH2 GVGDIFRKIVSTIKNVV-NH2 GVIDAAKKVVNVLKNLF-NH2 GILDVAKTLVGKLRNVLGI GIIDIAKKLVGGIRQVLGI GIDAKKVGGIRNLGI

deserticolin-1 signiferin-1 riparin-2.1

GLADFLNKAVGKVVDFVKS RLCIPYIIPC IIEKLVNTALGLLSGL-NH2

signiferin-1 signiferin-2.1 signiferin-2.2 signiferin-3.1 signiferin-4.1 signiferin-4.2 signiferin-4.3

RLCIPYIIPC IIGHLIKTALGMLGL-NH2 IIGHLIKTALGFLGL-NH2 GIAEFLNYIKSKA GFADLFGKVANLIKS GFADLFGKAVDFIKS GFADLFGKAVDFIKSRV

U. mjobergii

478

C. deserticola

C. riparia C. signifera

ref 124

252

254 253

residues including one D and two or three K or R residues that are important for their antimicrobial activity. According to analysis of the structures and activities of uperin 3.6, three K residues are necessary for antimicrobial activity.479 Uperins have an amphipathic α-helix with distinct hydrophobic and hydrophilic faces. Microbial killing by this peptide family has synergistic effects. For example, uperin 3.6 shows synergy against Gram-positive strains isolated from immunocomproAO


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Table 22. AMPs from Xenopus and Silurana Frogs source

name

sequence

X. laevis

ref 104, 490−493

PGQ magainin I magainin II PGLa CPF-1 CPF-2 CPF-3 CPF-4 XPF-1 XPF-2 PGLa-H

GVLSNVIGYLKKLGTGALNAVLKQ GIGKFLHSAGKFGKAFVGEIMKS GIGKFLHSAKKFGKAFVGEIMNS GMASKAGAIAGKIAKVALKAL-NH2 GLASFLGKALKAGLKIGAHLLGGTPQQ GLASFLGKALKAALKIGANMLGGTPQQ GLGSFLGKALKAALKIGANALGGSPQQ GLASLLGKALKAGLKIGTHFLGGAPQQ GWASKIGQTLGKIAKVGLQGLMQPK GWASKIGQTLGKIAKVGLKELIQPK KIAKVALKAL

CPF-C1 CPF-C2 XPF-C1 magaomom-C1 magaomom-C2

GFGSLLGKALRLG ANVL-NH2 GLGSLLGKALKFGLKAAGKFMGGEPQQ GWASKIGQALGKVAKVGLQQFIQPK GVGKFLHSAKKFGQALASEIMKS GVGKFLHSAKKFGQALVSEIMKS

CPF-B1 CPF-B2 CPF-B3 CPF-B4 XPF-B1 XPF-B2 PGLa-B1 PGLa-B2 magainin-B1 magainin-B2

GLGSLLGKAFKIGLKTVGKMMGGAPREQ GWASKIGTQLGKMAKVGVEFVQS GLGSLLGSLFKFIPKLLPSIQQ GLLTNVLGFLKKAGKGVLSGLLPL GFKQFVHSMGKFGKAFVGEIINPK GWASKIGTQLGKMAKVGLKEFVQS GMASKAGTIAGKIAKTAIKLAL-NH2 GMASKAGSIVGKIAKIALGAL-NH2 GKFLHSAGKFGKAFLGEVMIG GIGKFLHSAGKFGKAFLGEVMIG

magainin-AM1 magainin-AM2 PGLa-AM1 PGLa-AM2 CPF-AM1 CPF-AM2 CPF-AM3 CPF-AM4 XPF-AM1

GIKEFAHSLGKFGKAFVGGILNQ GVSKILHSAGKFGKAFLGEIMKS GMASKAGSVLGKVAKVAKLAAL-NH2 GMASTAGSVLGKLAKAVAIGAL-NH2 GLGSVLGKALKIGANLL-NH2 GIGSALAKAAKLVAGIV-NH2 GLGSVLGKILKMGANLLGGAPKGA GLGSLVGNALRIGAKLL-NH2 GWASKIAQTLGKMAKVGLQELIQPK

magainin-PG1 magainin-PG2 PGLa-PG1 CPF-PG1 CPF-PG2 CPF-PG3

GVGKFLHAAGKFGKALMGEMMKS GVSQFLHSASKFGKALMGEIMKS GMASKAGTIVGKIAKVALNAL-NH2 GFGSLLGKALKIGTNLL-NH2 GFGSFLGKALKAGLKLGANLLGGAPQQ GFGSLLGKALKAGLKLGANLLGGAPQQ

magainin-L1 magainin-L2 PGLa-L1 PGLa-L2 PGLa-L3 PGLa-L4 CPF-L1 CPF-L2 CPF-L3

GIGKFLHSAKKFGKAFVGEVMKS GISQFLHSAKKFGKAFAGEIMK GMASTAGSIFGKLAKTALGAL-NH2 GMASTAGSVLGKLAKVAIKAAL-NH2 GMASTAGSVLGKLAKVALGAL-NH2 GMASTVGSIFGKLAKTALGAL-NH2 GIGSLLAKAAKLGANLL-NH2 GIGSALAKAAKLVAGIL-NH2 GLGTFLGNALKTGLKIGANLL-NH2

magainin-P1 magainin-P2 PGLa-P1 CPF-P1

GIGKFLHSAGKFGKAFVGEIMKS GIGQFLHSAKKFGKAFVGEIMKS GMASTAGSIAGLIAVLKAL-NH2 GFGSFLGKALKAALKIGANALGGAPQQ

X. clivii

484

X. borealis

483

X. amieti

481

X. pygmaeus

105

X. lenduensis

105

X. petersii

105

AP


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name

sequence

CPF-P2 CPF-P3 CPF-P4 CPF-P5

GLASFLGKALKAGLKIGSHLLGGAPQQ GFGSFLGKALKAALKIGANVLGGAPQQ GFGSFLGKALKAALKIGANVLGGAPEQ GFGSFLGKALKAALKIGADVLGGAPQQ

magainin-AN1 magainin-AN2 XPF-AN1 XPF-AN2 PGLa-AN1 PGLa-AN2 CPF-AN1

GIKEFAHSLGKFGKAFVGGILNQ GVSKILHSAGKFGKAFLGEIMKS GWASKIGQTLGKMAKVGLQELIQPK GWVSKIGQTLGKMAKVGLQELIQPK GMASKAGSVLGKVAKVALKAAL-NH2 GMASKAGSVLGKLAKVALGAL-NH2 GFASVLGKALKLGANLL-NH2

magainin-M1 magainin-M2 tigerinin-M1 XPF-M1 CPF-M1 CPF-M2

GIGKFLHSAGKFGKAFIGEIMKS GFKQFVHSLGKFGKAFVGEMIKPK WCPPMIPLCSPF-NH2 GWASKIGQTLGKMAKVGLKDLIQA GLGSLLGKAFKFGLKTVGKMMAGAPREQ GLGSLLGKAFKFGLKTVGKMMAGAPREE

magainin-MW1 XPF-M1 PGLa-MW1 PGLa-MW2 CPF-MW1 CPF-MW2 CPF-MW3

GIGKFLHSAGKFGKAFLGEVMKS GWASKIGQTLGKLAKVGLKEFAQS GWASKAGSVLGKITKIAIGAL-NH2 GWASKAGAIAGKIAKTAIKIAL-NH2 GLGSLLGKAFKFGLKTVGKMMGGAPREQ GLGSLLGKAFKFGLKTVGKMMGGAPREE GLGSLLGKAFKFGLKTVGKMMGGAPR

maginin-SE1 PGLa-SE1 PGLa-SE2 CPF-SE1 CPF-SE2 CPF-SE3 XPF-SE1 XPF-SE2 XPF-SE3 XPF-SE4 PFQa

GLKEVLHSTKKFAKGFITGLTGQ GMATKAGTALGKVAKAVIGAAL-NH2 GMATAAGTTLGKLAKFVIGAV-NH2 GFLGPLLKLGLKGVAKVIPHLIPSRQQ GFLGPLLKLGLKGAAKLLPQLLPSRQQ GFLGSLLKTGLKVGSNLL-NH2 GLFLDTLKKFAKAGMEAVINPK GLASTIGSLLGKFAKGGAQAFLQPK GFWTTAAEGLKKFAKAGLASILNPK GVWTTILGGLKKFAKGGLEALTNPK FLGALLGPLMNLLQ-NH2

CPF-SP1 CPF-SP2 CPF-SP3 XPF-SP1 XPF-SP2 PGLa-SP1

GFLGPLLKLGLKGVAKVLPHLIPSRQQ GFLGPLLKLGLKGAAKLLPQLIPSRQQ GFLGSLLKTGLKVGSNLL-NH2 GFWSSALEGLKKFAKGGLEALTNPK GLASTIGSLLGKFAKGGAQAFLQPK GMATKAGTALGKVAKAVIGAAL-NH2

PGLa-ST XPF-ST1 XPF-ST2 XPF-ST3 CPF-ST1 CPF-ST2 CPF-ST3/XT-7 hepcidin 1

GMATKAGTALGKVAKAVIGAAL-NH2 GVWSTVLGGLKKFAKGGLEAIVNPK GLASTLGSFLGKFAKGGAQAFLQPK GVFLDALKKFAKGGMNAVLNPK GFLGPLLKLAAKGVAKVIPHLIPSRQQ GFLGSLLKTGLKVGSNLL-NH2 GLLGPLLKIAAKVGSNLL-NH2 SFICHRGHSASLSGNEVTVTGNQIPETQMEESNALEPLLRSKRQSHLSICVH

X. andrei

ref

482

X. muelleri

485

X. muelleri west

485

S. epitropicalis

107

S. paratropicalis

482

S. tropicalis

489, 494

the most common fate of AMP genes after polyploidization.482 However, PFQa with a unique sequence has been identified from S. epitropicalis. Of the Silurana AMPs, magainin-SE1 and PGLa-SE1 lack stable α-helical conformations despite being

very basic and have low antimicrobial potency. However, CPFSE2 and CPF-SE3 potently inhibit the growth of a range of S. aureus strains. Their significantly hemolytic properties preclude their use as systemic agents except as superficial agents in AQ


Chemical Reviews

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Table 23. AMPs from Hymenochirus and Amolops Frogs source

name

sequence

H. boettgeri

ref 495

hymenochirin-1B hymenochirin-2B hymenochirin-3B hymenochirin-4B hymenochirin-5B

IKLSPETKDNLKKVLKGAIKGAIAVAKMV-NH2 LKIPGFVKDTLKKVAKGIFSAVAGAMTPS IKIPAVVKDTLKKVAKGVLSAVAGALTQ IKIPAFVKDTLKKVAKGVISAVAGALTQ IKIPPIVKDTLKKVAKGVLSTIAGALST

temporin-CG1 temporin-CG2 temporin-CG3 temporin-CG4 temporin-CG5 esculentin-2CG1 palustrin-2CG1 brevinin-1CG1 brevinin-1CG2 brevinin-1CG3 brevinin-1CG4 brevinin-1CG5 brevinin-2CG1

FLPFVGNLLKGLL-NH2 FFPIVGKLLSGLF-NH2 FLPIVGKLLSGLF-NH2 FLPILGNLLNGLL-NH2 FLPFVGNLLNGLL-NH2 SLFSIFKTAAKFVGKNLLKQAGKAGLETLACKAKNEC GLWNTIKEAGKKFAINVLDKIRCGIAGGCKT FLSTALKVAANVVPTLFCKITKKC FLPIVAGLAANFLPKIVCKITKKC FLSTLLNVASNVVPTLICKITKKC FLSTLLNVASKVVPTLFC KITKKC FLPMLAGLAANFLPKIVCKITKKC GILDKLKEFGISAARGVAQSLLNTASCKLAKTC

brevinin-1-AJ1 brevinin-1-AJ2 brevinin-1-AJ3 brevinin-2-AJ1 brevinin-2-AJ2 brevinin-2-AJ3 brevinin-2-AJ4 brevinin-2-AJ5 brevinin-2-AJ6 brevinin-2-AJ7 esculentin-2-AJ1 esculentin-2-AJ2 esculentin-2-AJ3 esculentin-2-AJ4 odorranain-F-AJ-1 odorranain-F-AJ-2 temporin-AJ1 temporin-AJ2 temporin-AJ3 temporin-AJ4 temporin-AJ5 temporin-AJ6 temporin-AJ7 temporin-AJ8 temporin-AJ9 temporin-AJ10 temporin-AJ11 amolopin-3 ranacyclin-AJ jingdongin-1 jingdongin-2 jindongenin-1a palustrin-2AJ1 palustrin-2AJ2

FLPLAVSLAANFLPKLFCKITKKC FLSTLLKVAFKVVPTLFCPITKKC FLPLAVSLAANFLPKLFCKITKNVETLEMELEII GLMSTFKRVGISAIKGAAKNVLDVLSCKIAKTC GLMSTFKQVGISAIKGAAKNVLDVLSCKIAKTC GLMSTFKQVGISAIKGAAQNVLGVLSCKLAKTC GFMSTFKQVGISAIKGAAKNVLDVLSCKIAKTC GILSTLKQFGKAAVKGVAQSLLNTASCKLAKTC GILSTLKQFGKAAVKGVAQSFLNTASCKLAKTC GLVSTFKQVGISAIKGAAKNVLDVLSCKIAKTC GIFSIIKTAAKFLGKNLLKEAGKAGMEHLACKAKNEC GIFSLIKTAAKFVGKNLLKQAGKAGLEHLACKAKNEC GIFSLIKTAAKFVGKNLLKQAGKAGLEHLACKAENEC GILSLIKTAAKFVGKNLHKQAGKGGLEHLACKAKNEC GIMSKIKGTVQNAAVTLLNKLQCKITGGC GFMDTAKNVAKNVAVTLIDKLRCKVTGGC FLPIVTGLLSSLL FFPIGGKLLFGLL-NH2 FFPIVGKLLSGLL-NH2 FFPIVGKLLFGLL-NH2 FPPIVGKLLFGLL-NH2 FLPIVGKLLSGLL-NH2 FLPIVGKLPSGLL-NH2 FFPIVGKRLYGLL-NH2 FLPIVGKLLSGLTGLL-NH2 FLPIVGKLLSGLSGLL-NH2 FFPIGGKLLSGLTGLL-NH2 FLPPSPWKETFRTT AAFRGCWTKSYSPKPCLGKR FLPLFLPKIICVITKKC FLPIVENCSLVCWENNQKC DSMGAVKLAKLLIDKMKCEVTKAC GFMDTAKNVAKNVAVTLIDKLRCKVTGGC GFMDTAKQVAKNVAVTLIDKLRCKVTGGC

hainanenin-1 hainanenin-2 hainanenin-3 hainanenin-4 hainanenin-5

FALGAVTKLLPSLLCMITRKC FALGAVTKLLPSLLCMITRQC FALGAVTKLLPSPLCMITRKC FALGAVINLLPSLLCMITRKC FALGAVTKRLPSLFCLITRKG

A. chunganensis

500

A. jingdongensis

497, 501

A. hainanensis

498

AR


Chemical Reviews

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name

sequence

A. ricketti

ref 502

brevinin-1RTa brevinin-1RTb brevinin-1RTc brevinin-2RTa brevinin-2RTb

FLPLLAGVVANFLPQIICKIARKC FLGSLLGLVGKVVPTLFCKISKKC FLGSLLGLVGKIVPTLICKISKKC GLMSTLKDFGKTAAKEIAQSLLSTASCKLAKTC GILDTLKEFGKTAAKGIAQSLLSTASCKLAKTC

esculentin-2-ALa esculentin-2-ALb temporins-ALa temporins-ALb temporins-ALc temporin-ALd temporin-Ale temporin-Alf temporin-Alg temporin-Alh temporin-Ali temporin-Alj temporin-Alk brevinins-ALa brevinins-ALb brevinins-ALc brevinins-ALd amolopins amolopin-1a amolopin-1b amolopin-1c amolopin-1d amolopin-2a amolopin-2b amolopin-2c amolopin-2e amolopin-2f amolopin-2g amolopin-2h amolopin-2i amolopin-2k amolopin-3a amolopin-6a amolopin-6b amolopin-7a amolopin-8a amolopin-9a amolopin-9b amolopin-n1 amolopin-n2 amolopin-p1 amolopin-p2 ranacyclin-B-AL1 cathelicidin-AL

GIFALIKTAAKFVGKNLLKQAGKAGLEHLACKANNQC GIFSLIKTAAKFVGKNLLKQAGKAGVEHLACKANNQC FLPIVGKLLSGLSGLL-NH2 FLPIVGKLLSGLGLL-NH2 LLPIVGKLLSGLGLL-NH2 FLPIAGKLLSGLSGLL-NH2 FFPIVGKLLFGLSGLL-NH2 FFPIVGKLLSGLSGLL-NH2 FFPIVGKLLFGLFGLL-NH2 FLPIVGKLLSGLSGLS-NH2 FFPIVGKLLSGLL-NH2 FFPIVGKLLFGLL-NH2 FFPIVGKLLS-NH2 FLPMLAGLAANFLPKLFCKITKKC FLPLAVSLAANFLPKLFCKITKKC FLPLAVSLAANFLPELFCKITKKC FLPLAVSLAANLLPKLFCKITKKC NILSSIVNGINRALSFFG FLPMLAGLAANFLPKLFCKITKKC FLPLAVSLAANFLPKLFCKITKKC FLPMLAGLAANLLPKLFCKITKKC FLPMLAGLAANFLPELFCKITKKC FLPIVGKLLSGLSGLLGK FLPIVGKLLSGLLGK LLPIVGKLLSGLLGK FLPIAGKLLSGLSGLLGK FFPIVGKLLFGLSGLLGK FFPIVGKLLSGLSGLLGK FFPIVGKLLFGLFGLLGK FFPIVGKLLSGLLGK FFPIVGKLLFGLLGK FLPPSPWKETFRTT AARPPLGCKAAFC AARPPLRCKAAFC AAFRGCWTKNYSPKPCLGKR GARPPLRCKAALC GIFALIKTAAKFVGKNLLKQAGKAGLEHLACKANNQC GIFSLIKTAAKFVGKNLLKQAGKAGVEHLACKANNQC FFPIVGKLLSG FLPIVGKLLSGLSGLSKKKK NILSSIVNGINRALSFFG NVLSSVANGINRALSFFG AAFRGCWTKNYSPKPCL RRSRRGRGGGRRGGSGGRGGRGGGGRSGAGSSIAGVGSRGGGGGRHYA

A. loloensis

307, 496, 499

treatment of S. aureus skin infections and decolonization of S. aureus carriers.107 The hemolytic activity of the peptides can be reduced by designing analogs based on structure−activity studies. For example, potent, nonhemolytic analogs of the structurally related peptide XT-7 from S. tropicalis have been successfully developed.489 The analog [G4K] XT-7 has decreased helicity and hydrophobicity and increased cationicity;

it is nonhemolytic and maintains potent and broad-spectrum antimicrobial activity. 2.14.18. Hymenochirus. Hymenochirus, Xenopus, and Silurana belong to the amphibian family Pipidae. Five hymenochirins AMPs have been identified from H. boettgeri, which is the only member of the subfamily Pipinae.495 Hymenochirins have very low structural identity with reported peptides from the Silurana and Xenopus genera. Hymenochirins AS


Chemical Reviews

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Table 24. AMPs from Pelophylax, Limnonectes, Bufo, and Ceratophrys Frogs source

name

sequence

ref

P. saharic

505−507 temporin-1Sa temporin-1Sb temporin-1Sc temporin-SHf temporin-SHd

FLSGIVGMLGKLF-NH2 FLPIVTNLLSGLL-NH2 FLSHIAGFLSNLF-NH2 FFFLSRIF-NH2 FLPAALAGIGGILGKLF-NH2

esculentin-1P esculentin-2P brevinin-1P pelophylaxin-1 pelophylaxin-2 pelophylaxin-3 pelophylaxin-4

GIFSLIKGAAKVVAKGLGKEVGKFGLDLMACKVTNQC GIFSKLAGKKIKNLLISGLKNVGKEVGMDVVRTGIDIAGCKIKGEC FLPALIGIAAKALPSLLCKITKKC GILTDTLKGAAKNVAGVLLDKLKC GILLNTLKGAAKNVAGVLLDKLKCKITGGC GLMDSLKGLAATAGKTVLQGLLKTASCKLEKT ILPFLAGLFSKILGK-NH2

pelophylaxin-2GY temporin-1GY temporin-1KM nigrocin-1 nigrocin-2 pelophylaxin-2 esculetin-1P esculetin-2P

GLLLDTVKGAAKNVAGILLNKLKCKMTGDC VIPIVSGLLSSLL-NH2 FIPLVSGLFSRLL-NH2 GLLDSIKGMAISAGKGALQNLLKVASCKLDKTC GLLSKVLGVGKKVLCGVSGL GILLNTLKGAAKNVAGVLLDKLKCKITGGC GIFSKLAGKKIKNLLISGLKNVGKEVGMDVVRTGIDIAGCKIKGEC GIFSLIKGAAKVVAKGLGKEVGKFGLDLMACKVTNQC

gaegurin-RK1 gaegurin-RK2 gaegurin-RK3 gaegurin-RK4 gaegurin-LK1 gaegurin-LK2 gaegurin-LK3 gaegurin-LK4 temporin-LK1 rugosin-LK1 rugosin-LK2 rugosin-LK3 rugosin-LK4 rugosin-RK1 rugosin-RK2 rugosin-RK3 rugosin-RK4 nigroain-B-RK1 nigroain-C-RK1 nigroain-C-RK2 nigroain-D-RK1 nigroain-RK1 nigroain-RK2 nigroain-RK3 ranacyclin-B-LK1 ranacyclin-B-LK2

FIGPIIKIASSLLPTAICKIFKKC FIGPVLKIAAGILPTAICKGFKKC FLGPIIKMATGILPTAICKGLKKC FIGPVLKMATSILPTAICKGFKKC FIGPVLKMATSILPTAICKGFKKC FLGPIIKMATGILPTAICKGLKKC FIGPVLKIAAGILPTAICKGFKKC FIGPIIKIASSLLPTAICKIFKKC FFPLLFGALSSMMPKLF-NH2 SIRDKIKTMAIDLAKSAGTGVLKTLICKLDKSC SIRDKGKTIAIDLAKSAGTGVLKTLMCKLDKSC SIRDKIKTIAIDLAKSAGTGVLKTLICKLDKSR SIRDKIKTIAIDLAKSAGTGVLKTLICKLDKSC SIRDKIKTMAIDLAKSAGTGVLKTLICKLDKSC SIRDKGKTIAIDLAKSAGTGVLKTLMCKLDKSC SIRDKIKTIAIDLAKSAGTGVLKTLICKLDKSR SIRDKIKTTAIDLAKSAGTGVLKTLICKLDKSC DVQRRCVISAAWFHKIRCKLTGNC FKMWKRPPFQTSCSGGIKE FFPLLFGALSSMMPKLFGK CMHWQTGPARTSCIGP SALVGCWTKSWPPKPCFGRG SALVGCWTKSWPPKPCFGR SMLVGCWTKSYPPKPCFGRG SALVGCWTKSWPPKPCFGRG SALVGCWTKSWPPKPCFGR

limnonectin-1Fa limnonectin-1Fb

SFPFFPPGICKRLKRC SFHVFPPWMCKSLKKC

Lf-CATH1 Lf-CATH2

PPCRGIFCRRVGSSSAIARPGKTLSTFITV GKCNVLCQLKQKLRSIGSGSHIGSVVLPRG

buforin I buforin II ceratoxin

AGRGKQGGKVRAKAKTRSSRAGLQFPVGRVHRLLRKGNY TRSSRAGLQFPVGRVHRLLRK NVTPATKPTPSKPGYCRVMDELILCPDPPLSKDLCKNDSDCPGAQKCCYRTCIMQCLPPIFRE

P. plancyi fukienensis

503, 517

P. nigromaculatus

504

L. kuhlii

196, 510

L. fujianensis

509

L. fragilis

511

B. gargarizans

C. calcarata

518

AT

516


Chemical Reviews

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positive bacteria S. aureus and B. megaterium and the fungus A. flavus. In contrast, temporin-1Sc, which has a net positive charge similar to temporin-1Sa but with an H residue instead of K, does not kill Gram-negative bacteria and has a lower efficacy against the viability of Gram-positive bacteria. However, temporin-1Sc kills yeasts and fungus.505 The smallest natural linear AMP, temporin-SHf, contains a highly hydrophobic structure that includes 4 F residues in its primary structure of 8 residues, which is the highest percentage of any known peptide or protein. Like temporin-SHd from P. saharicus, temporin-SHf from the same species adopts a nonamphipathic α-helical structure in anionic membrane-mimetic environments that is stabilized by a compact hydrophobic core on one face that penetrates the micelle interior. Temporin-SHd and temporinSHf inhibit broad-spectrum Gram-positive and Gram-negative bacteria and yeasts and have no hemolytic activity. These peptides disrupt acyl chain packing of anionic lipid bilayers, damage the local integrity of microbial membranes, and cause leakage of intracellular components through a detergent-like effect. These results indicate that their antimicrobial activities are probably via a carpet mechanism.506,507 2.14.21. Limnonectes. Currently, at least 55 species are recognized in the genus of Limnonectes amphibians.508 AMPs have been found only in L. fujianensis, L. kuhlii, and L. fragilis (Table 24). The first AMPs reported in this genus were limnonectin-1Fa and limnonectin-1Fb from the skin secretions of L. fujianensis, which are also the only identified AMP family from this species. Although they are not hemolytic and ineffective against S. aureus and C. albicans, both limnonectins have relatively potent growth inhibitory activity against E. coli.509 AMPs from L. kuhlii mainly belong to the nigroain, gaegurin, ranacyclin, rugosin, and temporin families. Most strongly inhibit Gram-positive bacteria, Gram-negative bacteria, and fungi.510 In addition, ranacyclin-B-LK1 and ranacyclin-B-LK2 have trypsin-inhibitory activity. Lf-CATH1 and Lf-CATH2 belonging to the cathelicidin family are reported from L. fragilis. Both have 30 aa including two C residues that are conserved in the sequences of most known amphibian cathelicidins. According to homology modeling analysis, Lf-CATH1 and Lf-CATH2 have a conformation typical of small cationic cathelicidin peptides, which are mostly α-helix. Synthetic Lf-CATH1 and Lf-CATH2 potently inhibit a wide range of microorganisms in vitro with negligible cytotoxicity and hemolysis.511 2.14.22. Bufo. Although Bufo is a large genus of true toads in the amphibian family Bufonidae, only two AMPs, buforin I and buforin II, are reported from this genus (Table 24). Buforin I is a 39-aa AMP first identified from the stomach tissue of the Asian toad Bufo gargarizans that has stronger antimicrobial activities in vitro than magainin II against a range of microorganisms.512,513 The natural degradation product of buforin I is buforin II, a 21-aa AMP that inhibits microorganisms with higher potency than buforin I. The sequences of both buforin I and II contain the N-terminal region of the Xenopus histone H2A with DNA-binding activity and weak antimicrobial activity. Similar to many amphiphatic α-helical AMPs, buforin II adopts a helix-hinge-helix structure in 50% trifluoroenthanol and has N-terminal and C-terminal α-helices, which are separated by P11 and extend from residues R5 to F10 at the N-terminus and V12 to K21 in the C-terminus. Buforin II does not seem to inhibit microorganisms through membrane permeabilization because this peptide does not lyse cells but

have a relatively weak propensity to adopt a helical conformation in the conserved central region, whereas hymenochrin-1B has a strong propensity to form a stable and extended α-helical conformation. Hymenochirin-1B also has greater cationicity as compared to other hymenochirins. All synthetic hymenochirins show broad-spectrum antimicrobial activity and relatively weak hemolytic activity except hymenochirin-5, which has no hemolytic activity and cannot inhibit P. aeruginosa or K. pneumoniae growth. Hymenochirin1B has greater hemolytic activity than hymenochirin-2B and hymenochirin-3B, consistent with their content of stable αhelix.495 2.14.19. Amolops. The large amphibian group Amolops has 45 species worldwide. More than 100 AMPs have been identified from A. chunganensis, A. jingdongensis, A. hainanensis, A. ricketti, and A. loloensis. These AMPs belong to the families temporin, brevinin-2, brevinin-1, amolopin, hainanenin, palustrin-2, ranacyclin, jingdongin, odorranain-F, and esculentin-2 (Table 23). In addition, cationic cathelicidin-AL was also identified from A. loloensis. Cathelicidin-AL has 48 aa with 12 basic residues and no acidic residues even though its precursor contains the highly conserved anionic cathelin domain of a cysteine proteinase inhibitor before the AMP fragment at the C-terminus.496 Cathelicidin-AL has weak killing activity against B. subtilis and C. albicans with negligible hemolytic activity and no cytotoxicity and efficiently kills bacteria and some fungal species including clinically isolated drug-resistant microorganisms.496 Like many peptides from Ranadiae such as peptides in the families brevinin, esculentin, and ranatuerin, the hainanenins, jindongenin-1a, palustrin-2AJ1, and palustrin-2AJ2 contain a rana box that gives them similar structures and mechanisms of action.497,498 The amolopin family is found only in A. loloensis with no similarity to any peptides in any other known family. Circular dichroism spectroscopy shows that amolopin-p1 adopts a structure of random coil combined with β-sheet in water, Tris-HCl, or Tris-HCl-SDS.499 In contrast to the majority of other identified peptides in the esculentin-2 family, esculentin-2CG1 from A. chunganensis contains an S at its N-terminus instead of a G.500 Generally, AMPs from the Amolops genus strongly inhibited tested microorganisms including Gram-negative bacteria, Grampositive bacteria, and fungi and have little hemolytic activity.307,498−501 2.14.20. Pelophylax. Twenty AMPs have been characterized from several Pelophylax amphibians including P. saharica, P. saharicus, P. plancyi fukienensis, and P. nigromaculatus (Table 24). Most of these AMPs belong to families that are found in other amphibians such as temporin, brevinin-1, nigrocin, esculetin-1, and esculetin-2. Several AMPs named pelophylaxin 1−4 were identified from P. plancyi fukienensis. The nucleotide sequences of the four prepropelophylaxin openreading frames and the corresponding AMPs from Rana frogs share 75−95% similarity. The conserved preproregion of each pelophylaxin precursor contains a putative 22-residue signal peptide before an acidic peptide terminating in a typical KR convertase-processing motif.503 Another member of the pelophylaxin family, pelophylaxin-2GY, was isolated from P. nigromaculatus and inhibits E. coli.504 Small hydrophobic temporins from P. saharica differ markedly in their spectra of activity. Temporin-1Sa is highly active against Gram-negative and Gram-positive bacteria, yeasts, and fungi. Temporin-1Sb, like most temporins lacking a basic residue, has no antimicrobial properties or is weakly active against the GramAU


Chemical Reviews

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Table 25. AMPs from Lithobates Frogs source

name

sequence

ref

L. chiricahuensis

328, 524 esculentin-2CHa ranatuerin-2CHa ranatuerin 2CHb ranatuerin-2CHc brevinin-1CHa brevinin-1CHb palustrin-2CHa brevinin-1CHc

GFSSIFRGVAKFASKGLGKDLAKLGVDLVACKISKQC GLMDTVKNAAKNLAGQLLDRLKCKITGC GFLSTVKNLATNVAGTVIDTLKCKVTGGCRT GLMDTVKNVAKNLAGQLLDRLKCKITGC FLPIIAGVAAKVLPKLFCAITKKC FLPVIAGLAAKVLPKLFCAITKKC GLLSTFKNLATNVAGTVIDTLKCKVTGGCRT GNAEEERRRDGPDEMEQPGLPLLTGLAANLLRPIYCTITQNC

brevinin-1CPa esculentin-1CPa esculentin-2CPa ranatuerin-2CPa ranatuerin-2CPb ranatuerin-2CPc temporin-CPa temporin-CPb

FLPLVRVAAKLIPSVVCAISKRC GLFSKLNKKKIKSGLIKIIKTAGKEAGLEALRTGIDVIGCKIKGEC GFFSLIKGVAKIATKGLAKNLGKMGLDLVGCKISKEC GIMDTIKDTAKTVAVGLLDKIKCKITGC GIMDTIKNTAKTVAVGLLDKIKCKITGC GLMDTVKNAAKNLAGQLLDTIKCKITGC IPPFIKKVLTTVF-NH2 FLPIVGRLISGIL-NH2

brevinin-1Wa ranatuerin-2Wa ranatuerin-2 Wb esculentin-2Wa temporin-Wa

FLPVLARLAVKFLPSIVCAATKKC GIMDSIKGLGKNLAGQLLDKLKCKITGC GLFDSIKNVAKNVAAGLLDKLKCKITGC NIFSLLSLGAKVLGKTLLKSAGKAGAEQLACKATNQC FISKIASLGAGVLX

brevinin-1VLa brevinin-1VLb brevinin-1VLc brevinin-1VLd brevinin-1VLe ranatuerin-2VLa ranatuerin-2VLb ranatuerin-2VLc plaustrin-2Vla peptide RC12

FLGAIAGVAAKFLPKVFCFITKKC FLGAIAGVAAKVLPKVFCFITKKC FLPVIASVAAKVLPK VFCFITKKC FLPLIAGVAANFLPKIFCLISKKC FLPLIAGVAASILPKIFCFITKKC GIMDTIKGAAKDVAAQLLDKLKCKITKC GIMDTIKGAAKDLAGQLLDKLKCKITKC GIMDTIKGAAKDLAGELLDKLKCKITKC GLFDTIKNMATNVAGTMIDKLKCKVTGKC RICYAMWIPYPC

brevinin-1BLa brevinin-1BLb brevinin-1BLc

FLPAIVGAAAKFLPKIFCAISKKC FLPIIAGVAAKVLPKIFCAISKKC FLPIIAGIAAKFLPKIFCTISKKC

brevinin-1Ya brevinin-1Yb brevinin-1Yc ranatuerin-2Ya

FLPVIAGVAANFLPKLFCAISKKC FLPIIAGAAAKVVQKIFCAISKKC FLPIIAGAAAKVVEKIFCAISKKC GLMDTIKGVAKTVAASWLDKLKCKITGC

ranatuerin-2ONa temporin-ONa brevinin-1Ya brevinin-1Yb brevinin-1Yc

GLMDTVKNAAKNLAGQMLDKLKCKITGSC FLPTFGKILSGLF-NH2 FLPVIAGVAANFLPKLFCAISKKC FLPIIAGAAAKVVQKIFCAISKKC FLPIIAGAAAKVVEKIFCAISKKC

chensirin-2CBa catesbeianin-1 palustrin-2CBa palustrin-Ca brevinin-1CBa brevinin-1CBb temporin-1Cb temporin-1Cc temporin-CBa temporin-CBb

IIPLPLGYFAKKP LLRHVVKILEKYLGK GFLDIIKDTGKEFAVKILNNLKCKLAGGCPP GFLDIIKDTGKEFAVKILNNLKCKLAGGCPP FLGGLIKIVPAMICAVTKKC FLPFIARLAAKVFPSIICSVTKKC DVQVEKRFLFPLITSFLSKFLGK-NH2 DIQVEKRFLFPLIASFLGKVLGK-NH2 FLPIASLLGKYL-NH2 FISAIASMLGKFL-NH2

L. capito

528, 529

L. warszewitschii

528, 529

L. vaillanti

526

L. blairi

525

L. yavapaiensis

523, 525

L. onca

523, 529

L. catesbeianus

282,522,530,531

AV


Chemical Reviews

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name

sequence

ref

temporin-CBd temporin-CBf ranalexin ranacyclin Ca ranacyclin Cb ranacyclin Cc ranatuerin-1CBa ranatuerin-1CBb ranatuerin-2CBa ranatuerin-2CBc ranatuerin-2CBd ranatuerin-1Ca ranatuerin-1Cc ranatuerin-1Cd ranatuerin-2C ranatuerin-2RC ranatuerin-3 ranatuerin-5Ca ranatuerin-5Cb ranatuerin-7 ranatuerin-9

FISAIASFLGKFL-NH2 FLPIASMLGKYL-NH2 FLGGLIKIVPAMICAVTKKC SLRGCWTKSYPPQPCLGKR SLRGCWTKSFPPQPCLGKR SLRGCWTKSFPPQPCLGKRLNMN SMLSVLKNLGKVGLGFVACKINKQC SMFSVLKNLGKVGLGFVACKVNKQC GLFLDTLKGAAKDVAGKLEGLKCKITGCKLP GFLDIIKNLGKTFAGHMLDKIKCTIGTCPPSP GFLDIIKNLGKTFAGHMLDKIRCTIGTCPPSP SMFSVLKDLGKVGLGFVACKVNKQC SMFSVLKNLGKVGLGFVACKVSKQC TIFSVFKNWGKVGGGFGVCKFNKQC GVFLDTLKGLAGKMLESLKCKIAGCKP GLFLDTLKGAAKDVAGKLLEGLKCKITGCKP GFLDIINKLGKTFAGHMLDKIKCTIGTCPPSP DVQVEKRFLPIAPMLGKYLGK DVQVEKRFLPIASMLGKYLGK FLSAIASMLGKFL FLFPLITSFLSKVL

ranalexin-1Cb ranalexin-1Ca ranatuerin-1C ranatuerin-2Ca ranatuerin-2Cb temporin-1Ca temporin-1Cb temporin-1Cc temporin-1Cd temporin-1Ce

FLGGLMKAFPAIICAVTKKC FLGGLMKAFPALICAVTKKC SMLSVLKNLGKVGLGLVACKINKQC GLFLDTLKGAAKDVAGKLLEGLKCKIAGCKP GLFLDTLKGLAGKLLQGLKCIKAGCKP FLPFLAKILTGVL-NH2 FLPLFASLIGKLL-NH2 FLPFLASLLTKVL-NH2 FLPFLASLLSKVL-NH2 FLPFLATLLSKVL-NH2

palustrin-2AR palustrin-3AR ranatuerin-2ARa ranatuerin-2ARb esculentin-1ARa esculentin-1ARb temporin 1ARa brevinin-1ARa

GFISTVKNLATNVAGTVIDTIKCKVTGGC GIFPKIIGKGIVNGIKSLAKGVGMKVFKAGLNNIGNTGCNNRDEC GLMDTVKNAAKNLAGQLLDTIKCKMTGC GILDTIKNAAKTVAVGLLEKIKCKMTGC GIFSKINKKKAKTGLFNIIKTVGKEAGMDVIRAGIDTISCKIKGEC GLFPKFNKKKVKTGIFDIIKTVGKEAGMDVLRTGIDVIGCKIKGEC FLPIIGQLLSGLL FLPLVRVAAKILPSVFCAISKRC

ranatuerin-2TRa brevinin-1TRa brevinin-1TRb brevinin-1TRc ranatuerin-2TRb ranatuerin-2TRc

GIMDSIKGAAKEIAGHLLDNLKCKITGC FLPVIAGIAANVLPKLFCKLTKRC FLPFIASMAAKLVPKLVCAITKKC FLPVLAGIAANVLPTLICKLTRRC GILDTLKNVAKNVAAGLLDNIKCKITGC GIFDTIKNVAKNMAA LLDNIKCKITGC

brevinin-1Sa brevinin-1Sb brevinin-1Sc brevinin-1Sd

FLPAIVGAAGQFLPKIFCAISKKC FLPAIVGAAGKFLPKIFCAISKKC FFPIVAGVAGQVLKKIYCTISKKC FFPIAAAIAAKFFPKIFCATSKKC

brevinin-1SY

FLPVVAGLAAKVLPSIICAVTKKC

B2RP brevinin-1Spa brevinin-1Spb brevinin-1Spc brevinin-1Spd

GIWDTIKSMGKVFAGKILQNL-NH2 FFPIIAGMAAKLIPSLFCKITKKC FLPIIAGMAAKVICAITKKC FLPIIASVAAKLIPSIVCRITKKC FFPIIAGMAAKVICAITKKC

L. clamitans

532

R. areolata

533

L. tarahumarae/R. tarahumarae

534

L. sphenocephalus/R. sphenocephala

535, 536

L. sylvaticus/R. sylvatica

537

L. septentrionalis

48, 537, 538

AW


Chemical Reviews

Review


name

sequence

ranatuerin-2SPa ranatuerin-2SPb temporin-1SPa temporin-1SPb

GLFLNTVKDVAKDVAKDVAGKLLESLKCKITGCKS GLFLNTVKDVAKDVAKDVAGKLLESLKCKITGCKP FlSAITSILGKFF-NH2 FlSAITSILGKLL-NH2

brevinin-2Va brevinin-2Vb ranalexin-Va ranalexin-Vb ranaturein-2Va ranaturein-2Vb ranaturein-2Vc temporin 1Va temporin 1Vb temporin 1Vc

GLWDTLKNVGKAVLGKVLENV-NH2 SIWDTIKNVGKTVLGKVLEIV-NH2 FFGLHNLVPSMLCVVRKKC FLGGLFKLVPSVICAVTKKC GVFLDTLKGVGKDAAVKLLEALQCKFGVCKN GVFLDALKGVGKGVAVSLLNGLKCKLGVC GVFLNTIKEVGKDAAVKLLEALQCKFGVCKT FLSSIGKILGNLL-NH2 FLSIIAKVLGSLF-NH2 FLPLVTMLLGKLF-NH2

brevinin-1Pd brevinin-1Pe brevinin-1Pf brevinin-1Pg brevinin-1Ph brevinin-1Pi brevinin-1Pj brevinin-1Pl brevinin-1Pk brevinin-1PLa esculentin-2P peptide leucine arginine ranatuerin 2P ranatuerin-2Pc ranatuerin-2Pa ranatuerin-2Pb temporin-1P

FLPIIASVAANVFSKIFCAISKKC FLPIIASVAAKVFPKIFCAISKKC FLPIIAGIAAKFLPKIFCAISKKC FFPIVAGVAGQVLKKIFCTISKKC NAEEERRDGPDGKEETGIPLLPGLAANLCRPIYCTITKNC NAEEERRDGPDGKEETGIPLLPGLAANLCRPINC FFPNVASVPGQVLRKIFCAISKKC FLPIIAGMAAKFLPKIFCAISKKC FLPIIAGVAAKVFPKIFCTISKKC FFPNVASVPGQVLKKIFCAISKKC GFSSIFRGVAKFASKGLGKDLARLGVNLVACKISKQC LVRGCWTKSYPPKPCFVR GLMDTVKNVAKNLAGHMLDKLKCKITGC GLMDTVKNVAKNLAAHMLDKLKCKITGC GFLSTVKNLATNVAGTVIDTIKCKVTGGCRK SFLTTVKKLVTNLAALAGTVIDTIKCKVTGGCRT FLPIVGKLLSGLL

palustrin-2OLa peptide SA-14 ranalexin-Ola ranatuerin-2OLA temporin-1OLa temporin-1OLb

GFLDIIKDTGKDFAVKILNNLKCKLAGGCPR SLWNILKSMGRTLA FMGGIMKAIPAMICAMTKKC GLFVDTLKGLAGKMLESLKCKIAGCKP FLPFLKSILGKIL-NH2 FLPFFASLLGKLL-NH2

ranalexin-1G ranalexin-2G ranatuerin-1Ga ranatuerin-1Gb temporin-1Ga temporin-1Gb temporin-1Gc temporin-1Gd

FLGGLMKIIPAAFCAVTKKC GLLLDTLKGAAKDIAGIALEKLKCKITGCKP SMISVLKNLGKVGLGFVACKVNKQC GMFSVLKNLGKVGLGFVACKINKQC SILPTIVSFLSKVF-NH2 SILPTIVSFLSKFL-NH2 SILPTIVSFLTKFL-NH2 FILPLIASFLSKFL-NH2

ranalexin-Hka ranatuerin-2HKa temporin-1HKa

FLGGLIKIIPAAFCAVTKKC GLFLDTLKGAAKDIALEKLKCKITGCKP SIFPAIVSFLSKFL-NH2

brevinin-1Ba brevinin-1Bb brevinin-1Bc brevinin-1Bd brevinin-1Be brevinin-1Bf esculentin-2B

FLPFIAGMAAKFLPKIFCAISKKC FLPAIAGMAAKFLPKIFCAISKKC FLPFIAGVAAKFLPKIFCAISKKC FLPAIAGVAAKFLPKIFCAISKKC FLPAIVGAAAKFLPKIFCVISKKC FLPFIAGMAANFLPKIFCAISKKC GLFSILRGAAKFASKGLGKDLTKLGVDLVACKISKQC

L. virgatipes

ref

521

L. pipiens

206,415,539−541

L. okaloosae

542

L. grylio

87

L. heckscheri

542

L. berlandieri

79

AX


Chemical Reviews

Review


name ranatuerin-2B

sequence

ref

GLLDTIKGVAKTVAASMLDKLKCKISGC

2ONa from L. onca have similar MIC values at 50 μM;523,525 however, ranatuerin-2VLb from L. vaillanti shows relatively weak antimicrobial activity with an MIC higher than 75 μM.526 Temporin peptides have been widely identified in both New World and Eurasian Ranidae species and generally have extremely variable aa sequences.527 Like numerous temporins that deviate appreciably from the family consensus sequence FLPLIASLLSKLL-NH2, the aa sequence of temporin-Ona contains an extra hydrophilic T4 instead of L4 or I4, which might be the reason for its weak antimicrobial activity. Temporin-Ona is inactive against E. coli and has very low potency against S. aureus.523 Similarly, temporin-CPa from L. capito also has a poorly conserved consensus sequence with extra basic residues.528 Most temporin peptides inhibit only Gram-positive bacteria such as S. aureus,527 although temporinCPa is more potent against E. coli and C. albicans than S. aureus.528 Brevinin-1 peptides have been widely identified in both North American and Eurasian frogs; their primary structures are in Table 25. As compared to most brevinin-1 peptides, ranalexins are missing four residues. If ranalexins are correctly classified as brevinin-1 peptides, brevinin-1 peptides have been identified from skin secretions or extracts of all Lithobates frogs studied.529 Brevinin-1 peptides show particularly high antimicrobial potency. For instance, the MICs of brevinin-1VLa and brevinin-1VLc from L. vaillanti and brevinin-1BLc from L. blairi are lower than 3 μM against S. aureus and C. albicans.525,526 These peptides are also active against E. coli. Substitutions decreasing cationicity in brevinin-1VLd and brevinin-1VLe from L. vaillanti lead to loss of activity against E. coli. 526 N 11 substitutions of brevinin-1Ya and E 14 substitutions of brevinin-1Yc decrease cationicity and are the reason for the appreciably lower antimicrobial potencies of these AMPs from L. yavapaiensis.525 2.14.25. Odorrana. Among all amphibians studied, the genus Odorrana, which is from East Asia and surrounding regions and comprises 53 species,543 is generally reported to have the most abundant and diverse AMPs, even from an individual frog species (Table 26). For example, 107 AMPs belonging to 30 families have been characterized from O. grahami and 198 AMPs belonging to 97 different families have been characterized from the skin secretions of O. andersonii, O. margaratae, O. rotodora, and O. wuchuanensis.275,309 In addition, 728 cDNAs encoding different AMPs have been cloned from the skins of nine odorous frog species.275 This results in at least 800 different peptides from all AMP sequences currently reported in the 18 species of the genus Odorrana. In general, the primary structures of AMPs from Odorrana frogs show great variety in some families. Most peptides of the palustrin-2 family have two C-terminal aa and a core of 29 aa residues that include a cyclic heptapeptide domain. However, palustrin-2ISa from the skin of O. ishikawae contains only core 29 aa residues even though it is closely related to the palustrin proteins of American brown frogs, especially in the genus Lithobates. Palustrin-2ISb, also from O. ishikawae, is homologous to the palustrin-2 peptides of O. grahami but is structurally unique and contains 7 additional C-terminal aa. In addition,

strongly binds RNA and DNA across lipid bilayers. Thus, buforin II inhibits microorganisms by targeting intracellular components.512,514 In addition, buforin I and II are reported to have anticancer and antiendotoxin activities, making them promising candidates for pharmaceutical applications.515 2.14.23. Ceratophrys. Ceratoxin from the skin of C. calcarata is a unique AMP reported from Ceratophrys species (Table 24). Unlike most amphibian AMPs that have fewer than 50 aa and contain no or 1−2 Cs, ceratoxin contains eight C residues and 63 aa. Ceratoxin shares sequence identity with the toxin family of waprins that contain four disulfides and are found in snake venom. Recombinant ceratoxin strongly inhibits a wide range of microorganisms, and its MIC against S. aureus is 1.5 μg/mL.516 2.14.24. Lithobates. Many AMPs have been identified from the Lithobates genus that contains 49 species in North America, Central American, and South America including Southern Brazil; and frogs previously classified in the Lithobates (R. palmipes group), Pantherana, and Aquarana groups.519 These AMPs include B2RPs and members of the brevinin-1, esculentin-1, esculentin-2, ranatuerin-2, and temporin families (Table 25). The C-terminally α-amidated B2RP peptides from the skin secretions from L. septentrionalis and L. virgatipes are structurally related to brevinin-2 peptides, which have not been detected in any North American frogs of the Ranidae family.520,521 Unlike brevinin-2 peptides from Eurasian species, B2RP peptides lack the C-terminal cyclic heptapeptide domain. Furthermore, like the brevinin-1 and brevinin-2 AMPs, B2RPs lack a well-defined secondary structure in water. However, B2RP and an analog with residue substitutions from L. septentrionalis adopt a stable α-helical conformation with low amphipathicity in a membrane-mimetic environment. The B2RP peptides show moderate hemolytic activity and broadspectrum antimicrobial activity.520 Increasing amphipathicity and hydrophobicity increases hemolytic activity without increasing antimicrobial ability. A substitution that increases both cationicity and amphipathicity at the same time decreases both hemolytic activity and antimicrobial potency. However, increasing the cationicity of B2RP while maintaining amphipathicity increases antimicrobial potency without substantially changing hemolytic activity.520 Ranatuerin-2 peptides were first identified in the skin of L. catesbeianus and have been reported in 14 North American frogs in the genus Lithobates.522 These peptides generally contain a C-terminal cyclic hexapeptide domain, although their primary structures have low identity among species. For example, ranatuerin-2Ona from the skin secretions of L. onca includes a C-terminal cyclic heptapeptide domain but has poor structural identity to palustrin-2 peptides that also contain a cyclic heptapeptide domain and are produced by the closely related frog L. areolata.523 The poorly conserved primary structure among species of ranatuerin-2 peptides leads to very different antimicrobial properties and hemolytic activities. For example, ranatuerin-2 peptides from different Lithobates frogs have different MIC values against E. coli. Ranatuerin-2CHa and ranatuerin-2CHb from L. chiricahuensis have an MIC of 20 μM,524 ranatuerin-2Ya from L. yavapaiensis and RanatuerinAY


Chemical Reviews

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Table 26. AMPs from Odorrana Frogs source

name

sequence

O. schmackeri

ref 505, 517, 545, 546

esculentin-1S esculentin-2S brevinin-1HS1 brevinin-1HS2 brevinin-2HS1 brevinin-2HS2 brevinin-2HS3 brevinin-1S nigrocin-2S nigrocin-2SCb nigrocin-2SCa nigrocin-2SCc

GLFSKFAGKGIKNMIIKGIKGIGKEVGMDVIRTGIDVAGCKIKGEC GLFTLIKGAVKMIGKTVAKEAGKTGLELMACKVTNQC VIPFVASVAAEMMQHVYCAASKKC FLPLIASVAANLAPKIICKITKTC GLWDTIKQAGKKIFLSVLDKIRCKVAGGC SLLGTVKDLLIGAGKSAAQSVLKGKSCKLSKDC S1LGTVKDLLIGAGKSAALSVLKGKSCKLSKDC FFPAILRVAAKVGPAVLCAITKKC GILSGILGAGKSLVCGLSGLC GILSGVLGMGKKIVCGLSGLC GILSGILGAGKSLVCGLSGLC GILSNVLGMGKKIVCGLSGLC

temporin-HN1 temporin-HN2 vrevinin-1HN1 brevinin-1V brevinin-2HS2 odorranain-A6 odorranain-B1

AILTTLANWARKFL-NH2 NILNTIINLAKKIL-NH2 FLPLIASLAANFVPKIFCKITKKC FLPLIASVAANLVPKIFCKITKKC SLLGTVKDLLIGAGKSAAQSVLKGLSCKLSKDC VVKCSYRPGSPDSRCK AALKGCWTKSIPPKPCFGKR

nigrosin-OT tiannanensin pleurain-E-OT brevinin-1-OT2 brevinin-1v brevinin-1OT1 odorranain-A6 odorranain-B1 odorranain-G-OT odorranain-A-OT odorranain-C7HSa odorranain-C-OT1 odorranain-C-OT2 odorranain-C-OT3 odorranain-M-OT odorranain-P-OT margaretaein-OT1 margaretaein-OT2 lividin-OT esculentin-1v esculentin-2v esculentin-2-OT

SILSGIFGVGKKIVCGLSGLC AILTTLANWARKFL ATAWRMPPNGIPPIVAVRIRPLCGTV FLPLIASLAANFVPKIFCKITKKC FLPLIASVAANLVPKIFCKITKKC FLPLIASVAANLVPKIFCKKTKKC VVKCSYRPGSPDSRCK AALKGCWTKSIPPKPCFGKR FVPAILCSILKTC VVKCSFRPGSPAPRCK SLLGTVKDLLIGAGKSAAQSVLKGLSCKLSKDC SLLGTVKDLLIGAGKSAAQSVLKGLSCKLFKDC SLLGTVKDLPIGAGKSAAQSVLKGLSCKLSKDC SLLGTVKDLLIGTGKSAAQSVLKGLSCKLSKDC ATAWDFGPHGLRPIRPIRPTRIRPLCGKDKS VLPFVASVAAEMMQHVYCAASKKC CGYRHGKANCGKG CGYRHGNANCGKG AVPLIYNRPSIYVTKRPKGK GIFSKFAGKGIKDLIIKGVKGIAKEAGMDVIRTGIDIAGCKIKGEC GIFTLFKGAAKLLGKTLAKEAGKTGLELMACKVTNQC GIFTLFKGAAKLLGKTLAKETGKTGLELMACKVTNKC

palustrin-2ISb palustrin-2ISa palustrin-2ISc palustrin-2ISd esculentin-1ISa esculentin-1ISb esculentin-2ISa brevinin-1ISa brevinin-2ISa brevinin-2ISb brevinin-2ISc nigrocin-2ISa nigrocin-2ISb nigrocin-2ISc odorranain-MISa ishikawain-1

GLWNSIKIAGKKLFVNVLDKIRCKVAGGCKTSPDVE GFMDTAKNVAKNVAVTLLDKLKCKITGGC GFMDTAKNVAKNVAATLLDKLKCKITGGC GFMSTASNVLTNVAGTVMDKLKCKFTGAC GIFSKFAGKGIKNLLVKGVKNIGKEVGMDVIRTGIDIAGCKIKGEC RIFSKIGGKAIKNLILKGIKNIGKEVGMDVIRTGIDVAGCKIKGEC GIFSLIKGAAKLITKTVAKEAGKTGLELMACKVTNQC FLPGVLRLVTKVGPAVVCAITRNC SLLDTFKNLAVNAAKSAGVSVLNALSCKISRTC SFLTTFKDLAIKAAKSAGQSVLSTLSCKLSNTC SVLGTVKDLLIGAGKSAAQSVLTTLSCKLSNSC GIFSTVFKAGKGIVCGLTGLC GILGTVFKAGKGIVCGLTGLC GILSTVFKAGKGIVCGLSGLC ATAWNLGPHGLRPIRPIRIRPLCGKDKS AAGYPFGIKV

O. hainanensis

548

O. tiannanensis

552

O. ishikawae

544, 550, 553

AZ


Chemical Reviews

Review


name

sequence

ishikawain-2 ishikawain-3 ishikawain-4 ishikawain-5 ishikawain-6 ishikawain-7 ishikawain-8

AAIYPFGIKIRCKAAFC NFYEIFRNRGGLIKDAATPWLPCEILRPC NIFEIFRNRNGGLIKDAATPWLPCEILRPC SPYRCGSPDSRGSENTRCLIKK RLMKCYKPNSRGFQLCE CGYRHGRLNCGRG GIFSVLNEVCKKNDYKPEICAHFSQNKP

nigrocin-2VB brevinin-1V brevinin-1Vb esculentin-1V esculentin-1Vb esculentin-2V esculentin-2Vb palustrin-1c palustrin-3b ranatuerin-2Va ranatuerin-2Vb temporin-1V temporin-1VE

SILSGNFGVGKKIVCGLSGLC FLPLIASVAANLVPKIFCKITKKC FLPLIAGLAANFLPKIFCAITKKC GIFSKFAGKGIKDLIIKGVKGIAKEAGMDVIRTGIDIAGCKIKGEC GIFTKINKKKAKTGVFNIIKTIGKEAGMDVIRAGIDTISCKIKGEC GIFTLFKGAAKLLGKTLAKEAGKTGLELMACKVTNQC GLFSILKGVGKIAIKGLGKNLGKMGLDLVSCKISKEC ALSILRGLEKLAKMGIALTNCKATKKC GIFPKIIGKGIKTGIVNGIKSLVKGVGMKVFKAGLSNIGNTGCNEDEC GLLDTIKNTAKNLAVGLLDKIKCKMTGC GIMDTVKGVAKTVAASLLDKLKCKITGC FLPLVGKILSGLIGK FLPLVGKILSGLI-NH2

brevinin-2JD brevinin-1JDa brevinin-1JDb brevinin-1JDc nigrocin-2JDa nigrocin-2JDb esculentin-2JDa esculentin-2JDb

GLLDTFKNLALNAAKSAGVSVLNSLSCKLSKTC FLPAVIRVAANVLPTVFCAISKKC FLPAVLRVAAQVVPTVFCAISKKC FLPAVLRVAAKVVPTVFCLISKK GIFGKILGAGKKVLCGLSGLC GIFGKILGVGKKVLCGLSGMC GLFTLIKGAAKLIGKTVAKEAGKTGLELMACKITNQC GIFTLIKGAAKLIGKTVAKEAGKTGLELMACKITNQC

brevinin-1HSa brevinin-1HSb esculentin-1HSa esculentin-2HSa brevinin-2HSa brevinin-2HSb nigrocin-2HSa nigrocin-2HSb

FLPAVLRVAAKIVPTVFCAISKKC FLPAVLRVAAQVVPTVFCAISKKC GIFSKFGGKAIKNLFIKGAKNIGKEVGMDVIRTGIDVAGCKIKGEC GIFSLIKGAAQLIGKTVAKEAGKTGLELMACKVTKQC GLLDSLKNLAINAAKGAGQSVLNTLSCKLSKTC GLLDTLKNMAINAAKGAGQSVLNTLSCKLSKTC GLLGSLFGAGKKVACALSGLC GLLGSIFGAGKKIACALSGLC

brevinin-1E-OG1 brevinin-1E-OG2 brevinin-1E-OG3 brevinin-1E-OG4 brevinin-1E-OG5 brevinin-1E-OG6 brevinin-1E-OG7 brevinin-1E-OG8 brevinin-2E-OG1 brevinin-2E-OG2 brevinin-2E-OG4 brevinin-2E-OG5 brevinin-2E-OG6 brevinin-2E-OG7 brevinin-2GRa brevinin-2GRb brevinin-2GRc esculentin-1-OG1 esculentin-1-OG2 esculentin-1-OG3 esculentin-1-OG4

FLPLLAGLAANFLPKLFCKITKKCRNFGNGIGNHLMWNII FLPLLAGLAANFLPKLFCKITRKG FLPLLAGLAANFLPKLFCKITKKC FLPFLAGLAANFLPKLFCKITRKC FLPLLAGLAANFLPKLFCKITRKC FLPLLAGLAANFLPKIFCKITKKC FFPLIAGLAANFLPQILCKIARKC FLPLLAGLAANFLPKLFCKITAKKKKKKK GLLDTFKNMALNAAKSAGVSVLNALSCKLSKTC GLLDTFKNLALNAPKSAGVSVLNSLSCKLSKTC GLLDTFKNLALNAAKSAGVSVLNSLSCKLFKTC GLLDTFKNLALNAAKSAGVGTEFIIL GLLDTFKNLALNAAKSAGVSVLNSLSCKLSKTC GLLDTFKNMALNAAKSAGVSVLNSLSCKLSKTC GLLDTFKNLALNAAKSAGVSVLNSLSCKLSKTC GVLGTVKNLLIGAKGSAAQSVLKTLSCKLSNDC GLFTLIKGAAKLIGKTVAKEAGKTGLELMACKITNQC GLFSKFAGKGIKNFLIKGVKHIGKEVGMDVIRTRIDVAGCKIKGEC GLFSKFAGKGIKNFLIKGVKHIGKEVGMDVIRTGIDVAGCKIKGEC GLFSKFAGKGIKNFLIKGVKHIGKEVGLDVIRTGIDVAGCKIKGEC GLFSKFAGKGIKDLIFKGVKHIGKEVGTDVIRTGIDVAGCKIKGEC

O. versabilis

ref

517, 551

O. jingdongensis

554

O. hosii

415

O. grahami

309, 547, 555−557

BA


Chemical Reviews

Review


name esculentin-1-OG5 esculentin-1-OG6 esculentin-1-OG7 esculentin-1-OG8 esculentin-1-OG9 esculentin-1-OG10 esculentin-1-OG11 esculentin-2-OG1 esculentin-2-OG2 esculentin-2-OG3 esculentin-2-OG4 esculentin-2-OG5 esculentin-2-OG6 esculentin-2-OG7 esculentin-2-OG8 esculentin-2-OG9 esculentin-2-OG10 esculentin-2-OG11 esculentin-2-OG12 esculentin-2-OG13 esculentin-2-OG14 esculentin-2-OG15 esculentin-2-OG16 grahamin-2 GRa nigrocin-OG1 nigrocin-OG2 nigrocin-OG3 nigrocin-OG4 nigrocin-OG5 nigrocin-OG6 nigrocin-OG7 nigrocin-OG8 nigrocin-OG9 nigrocin-OG10 nigrocin-OG11 nigrocin-OG12 nigrocin-OG13 nigrocin-OG15 nigrocin-OG16 nigrocin-OG17 nigrocin-OG18 nigrocin-OG19 nigrocin-OG20 nigrocin-OG21 nigrocin-OG22 nigrocin-OG23 nigrocin-OG24 nigrocin-OG25 nigrocin-OG26 nigrocin-OG27 nigrocin-OG28 nigrocin-OG29 nigrocin-OG30 nigrocin-OG31 nigrocin-2GRa nigrocin-2GRb nigrocin-2GRc odorranain-A1 odorranain-A2 odorranain-A3 odorranain-A4

sequence

ref

GLFSKFAGKGIKDLIFKGVKHIGKEVGMDVIRTGIDVAGCKIKGEC GLFSKFAGKGIKDLIFKGVKHIGKEVGMDVIRTGIDVAGRKIKGEC GLFSKFAGKGIKIF GLFSKFAGKGIKDLIFKGVKHIGKEVGMDVIRTGIDAAGCKIKGEC GLFSKFAGKGIKNFLIKGVKHIGKEVGMDVIGTGIDVAGCKIKGEC GLFSKFAGKGIKNFLIKGVKHIGKEVGMDVIRTGIDVAGCKIKGVC GLFSKFAGKGIKNFLIEGVKHIGKEVGMDVIRTGIDVAGCKIKGEC GLFTLIKGAAKLIGKTVAKEAGKTGPELMACKITNQC GLFTLIKGAAKLIGKTVAKEAGKTGLELMACKITHQC GLFTLIKDAAKLIGKTVAKEAGKTGLELMACKITNQC GFFTLIKGAAKLIGKTVAKEAGKTGLEIMACKITNQC GLFTLIKGAAKLIGRTVAKEAGKTGLELMACKITNQC GLFTLIKGAAKLIGKTVVKEAGKTGLELMACKITNQC GGLFTLIKGAAKLIGKTVAKEAGKTGLELMACKITNQC GIFSILKIATKLIGKTLAKAAGKAGAELAACKAANQC GLFTLIKGAAKLIGKTVAKKAGKTGLELMACKITNQC GLFTLIKGAAKLIGKTVAKEAGKTGLELMACKITNQC GLFTLIKGAAKLIGKTVAKEAGRTGLELMACKITNQC GLFTLIKGAAKLIGKIVAKEAGKTGLELMACKITNQC GPFTLIKGAAKLIGKTVAKEAGKTGLELMACKITNQC GLFTLIKGAAKLIGKTAAKEAGKTGLELMACKITNQC GLFTLIKGAAKLIGKAVAKEAGKTGLELMACKITNQC GLFTLIKGAAKSIGKTVAKEAGKTGLELMACKITNQC GLLSGILGAGKHIVCGLSGLC GLLSGILGAGKHVVCGLSGLC GLLGKILGVEKKVLCGLSGMC GLLSGILGVGKHIVCGLSGLC GLLSGILGAGKHIICGLSGLC GLLSGILGAGKQKVCGLSGLC GLLSGILGTGKHIVCGLSGLC GLLSGILGAGKHIVCGLSWLC GLLSGILGAGKHIVCGLSRLC GFLSGILGAGKHIVCGLSGLC GLLSGILGAGKNIVCGLSGLLKLESEII GLLKGILGAGKHIVCGFSGLC GPLSGILGAGKHIVCGLSGLC GLLSGILSAGKHIVCGLSGLC GLLRGILGAGKHIVCGLSGLC GLLSGILGAGEHIVCGLSGLC GLLSGILGAGKNIVCGLSGLC GLLSGILGAGKNIVCGLSGPC GLLSGILGAGKHTVCGLSGLC GLLSGILGAGKHIVCGLSGLC GLLSGVLGVGKKVLCGLSGLC GLLSKILGVGKKVLCGLSGMC GLLSGVLGVGKKVVCGLSGLC GLLSGILGAGKHIVCRLSGLC GFLSGILGAGKHIVCGLSGVC GLLSGVLGAGKHIVCGLSGLC GLLSGTLGAGKNIVCGLSGLC GLLSGIPGAGKHIVCGLSGLC GLLSGILGAGKHIVCGLGGLC GLLSGILGAGTNIVCGLSGLS GLLSGVLGVGKKVPCGLSGLC GLLSGILGAGKHIVCGLSGLC GLFGKILGVGKKVLCGLSGMC GLLSGILGAGKNIVCGLSGLC VVKCSSRLGSPDSRCN VVKCSYQLGSPDSRCN VVKCSYRLGSPDSRCN VVKCSYRPGSPDSRCK BB


Chemical Reviews

Review


name odorranain-A5 odorranain-A6 odorranain-A7 odorranain-A8 odorranain-B1 odorranain-B2 odorranain B6 odorranain-C1 odorranain-C10 odorranain-C2 odorranain-C3 odorranain-C4 odorranain-C5 odorranain-C6 odorranain-C7 odorranain-C8 odorranain-C9 odorranain-D1 odorranain-E1 odorranain-F1 odorranain-F2 odorranain-G1 odorranain-H1 odorranain-H2 odorranain-H4 odorranain-H5 odorranain-I1 odorranain-J1 odorranain-J2 odorranain-K1 odorranain-K2 odorranain-L1 odorranain-L2 odorranain-L3 odorranain-L4 odorranain-M1 odorranain-M2 odorranain-M3 odorranain-N1 odorranain-O2 odorranain-O3 odorranain-P1a odorranain-P1b odorranain-P1c odorranain-P 1d odorranain-P1e odorranain-P1g odorranain-P1h odorranain-P2a odorranain-Q1 odorranain-Q2 odorranain-R1 odorranain-S1 odorranain-T1 odorranain-T2 odorranain-U1 odorranain-V1 odorranain-V2 odorranain-W1 odorranain-W2 OGA1

sequence

ref

VVKCSYREGSPDSRCK VVKCSYRPGSPDSRCK VVKCSYREGSADSRCK VFKCYKPDSRGFQVCE AALKGCWTKSIPPKPCFGKR AALKGCWTKSIPPKPCFRKR AALRGCWTKSIPPKPCSGKR GVLGAVKDLLIGAGKSAAQSVLKTLSCKLSNDC GVLGTVKDLLIGAGKSAARVC GVLGTVKNLLIGTGKSAAQSVLKTLSCKLSNDC GVLGTVKNLLIGAGKSAAQSVLETLSCKLSNDC GVLGTVKDLLIGAGKSAAQSVLKILSCKLSNDC GVPGTVKDLLIGAGKSAAQSVLKALSCKLSNDC GVLGTVKNLLIGAGKSAAQSVLKTLSCKLFNDC GVLGTVKDLLIGAGKSAAQSVLKTLSCKLSNDC GVLGTVKNLLIGAGKSAAQSVLKTLSCKLSNDC GVLGTVKDLLIGAGKSAAQSVLKTLSCKLFNDC GFLDTFKNLALNAAKSAGVSVLNSLSCKLFKTC GLGGAKKNFIIAANKTAPQSVKKTFSCKLYNG GFMDTAKNAAKNVAVTLLDNLKCKITKAC GFMDTAKNVAKNVAVTLLDNLKCKITKAC FMPILSCSRFKRC GLFGKILGVGKKVLCGLSGMC GIFGKILGVGKKVLCGLSGVC GIFGKILGVGKKVPCGLSGMC GIFGKILGVGKKVLCGLSGMW GFFTLIKAANKLINKTVNKEAGKGGLEIMA GLFTLIKCAYQLIAPTVACN GLFTFIKCAYKLRAPAVACN GLFTLIKGAAKLIGKTVPKKQARLGMNLWLVKLPTNVKT GLFTLIKGAAKLIGKTVAKEAGRLGLNLWLVKLPTNVKT VEVQVRAVGIQGLSPLRQPAP VEVQVRDKGKGIYGLSPLRQPAP VEVQVREVGIQGLSPLRQPAP VEVQVRDKGKGIYGLSPLRQPTP ATAWDFGPHGLLPIRPIRIRPLCG ATAWDFGPHGLLPIRPIRIRPLCGKDKS ATALGLSSRGLLPIGFMFKDTIRCRKY DEKGPKWKR AVPLIYNPPGIYATKDQKENNLLEII GADEEDGGEAKLEDIKRAVPLIYNRPGIYAPKRPKGK VIPFVASVAAETMQHVYCAASKKMLKLNWKSSDVENHLAKC VIPFVASVAAEMMQHVYCAASKKC VIPSVASVAAEMMQHVYCAASKKC VIPFVASVAAEMMQPVYCAASKKC VIPFVASVAAEKMQHVYCAASKKC VIPFVASVAAEMMQHVYCAASKKR VIPFVASVAAEMMQHVYCAASKKMLKLNWKSSDVENHLKC GLLSGILGAGKHIVCGLSGPCQSLNRKSSDVEYHLAKC APFRMWYMYHKLKDMEPKPMA APFCLGYLSPKLKDMEPKPRG GFSPNLPGKGLRIS FLPPSPWKETFRTS TSRCYIGYRRKVVCS TSRCYIEYRRKVVCS GCSRWIIGIHGQICRD GLLSGTSVRGSI GLLMASSVRGRT GLFGKSSVWGRKYYVDLAGCAKA GLLRASSVWGRKYYVDLAGCAKA CGYKHGRANCGRG BC


Chemical Reviews

Review


name

sequence

OGB1 OGC1 OGC2 OGF1 OGF2 OGG1 palustrin-OG1 palustrin-OG2

ICLLVQARVRPRVCLKHYLVNFLTIVKT AIGNILKTLGNLAQKILGKQPKMLKLWKWNWKSSDVEYHLAKC AIGNILKTLGNLAQKILGK GLLRPPRCGEAYSMWT GLLSGPRCGEESTMWT GLLSGILGAGKHIVCGLTGCAKA GFWDTIKQAGKKFFLNVLDKIRCKVAGGCRT GLWDTIKQAGKKFFLNVLDKIRCKVAGGCRT

nigrocin-2HJ

GLLSKVLGVGKKVLCGVSGLC

lividin-1 lividin-2 lividin-2a lividin-2b lividin-3 lividin-4 Lividin-4a lividin-5 lividin-6 lividin-7a lividin-7b lividin-8 lividin-9a lividin-9b lividin-9c lividin-10 lividin-11 lividin-12 lividin-13 lividin-14 lividin-15 lividin-16 nigrocin-2LVa nigrocin-2LVb

ILPFVAGVAAEMMQHVYCAASKKC SFLDTLKNLAISAAKGAGQSVLSTLSCKLSKTC GLLDTIKNMALNAAKSAGVSVLNTLSCKLSKTC GLLDPIKNMALNAAKSAGVSVVNTLSCKLSKTC SVLGTVKDLLIGAGKSAAQSVLTALSCKLSNSC GVFTLIKGATQLIGKTLGKELGKTGLELMACKITNQC GVFTLIKGATQLIGKTLGKELGKTGLELMACKITKQC AALRGCWTKSIPPKPCPGKR GLMDAAKNVAKNVAATLLDKLKCKITGGC GILSGILGVGKKLVCGLSGLC GILSGLLGAGKKIVCGLSGLC AVPLIYNRPGIYVTKRPKGK SRVVKCIGFRPGSLDSRQSC SRVVKCIGFRPGSPDSRQSC SRVVKCIGFRPGSPDSRRSC GIFSKISGKAIKNLFIKGAKNVGKEVGMDVVRTGIDVVGCKIKGEC GFMDTAKNVAKNVAATLLDKLKCKITGGC AVKLPFRCKAVFC RLFKCYGPNSRGFQICE AMRLTYNRPCIYATKRTKEM MAFHETLARCALYGEC TSRCYVYRLKVVCS GLLSKVLGVGKKVLCGVSGLC GILSGILGMGKKLVCGLSGLC

O. hejiangensis

ref

546

O. livida

558

than a heptapeptide. Furthermore, its C-terminal AKA fragment is different from other amphibian AMPs.547 Temporin peptides with C-terminal amidation are extensively found in amphibian skin but identified only from O. versabilis and O. hainanensis in Odorrana frogs. Furthermore, the N-terminal aa of the two temporins from O. hainanensis are different. The A in temporin-HN1 and the N in temporin-HN2 appear only in tiannanensins from O. tiannanensis and temporin-1Lb from R. luteiventris.541,548 In contrast to temporins from Odorrana, odorranain, brevinin-1, and brevinin-2 peptides are highly conserved among Odorrana species. For example, mature peptides of brevinin-1 V, brevinin-2HS2, odorranain-A6, and odorranainB1 isolated from O. hainanensis are highly similar to AMPs from O. schmackeri, O. versabilis, and O. grahami.309,543,545,548,549 AMPs from O. ishikawae are closely related to AMPs from O. grahami and O. hosii according to the similarity of their esculentin-1, esculentin-2, palustrin-2, brevinin-2, and nigrocin2 peptides. For example, esculentin-1ISa and esculentin -1ISb from O. ishikawae are identical to esculentin-1-OG1 from O. grahami and esculentin-1HSa from O. hosii. Esculentin-2ISa from O. ishikawae is identical to brevinin-2GRc from O. grahami, esculentin-2HSa from O. hosii, and lividin-4 from O. livida, and distinct from esculentin-2VEb from O. versabilis.550

sequence identity among core residues of palustrin-2ISa and palustrin-2ISb is relative low at 41.4%.544 Like the nigrocin-2 peptide prototypes, a lack of helicity in aqueous environments but a high degree of helicity in membrane-mimetic environments is seen in nigrocin-2HJ from O. hejiangensis, nigrocin-2LVa and b from O. livida, nigrocin-2-related peptides from O. grahami, nigrocin-2SCa−c from O. schmackeri, and nigrocin-2VB from O. versabilis.309 These nigrocin-2 peptides contain a rana box at their Cterminis, which is unusual because it lacks basic aa and highly hydrophobic features. The rana box also appears in brevinin1HS1, brevinin-1HS2, brevinin-2HS1, brevinin-2HS2, and brevinin-2HS3 from the skin secretions of the Chinese piebald odorous frog, O. schmackeri.545 In addition, nigrocin-2 peptides from O. schmackeri, O. livida, O. hejiangensis, and O. versabilis can be considered G/L-rich brevinin orthologs because they share the G/L-rich feature with the plasticins.546 Odorranin-NR from O. grahami shares similarity with the nigrocin family, in particular, an N-terminal 14 aa fragment that is highly conserved. However, as compared to the intramolecular disulfide-bridged segment at the C-terminal region of nigrocins, brevinin, esculentin, and odorranains-C, H, and P, the corresponding region of odorranain-NR is a hexapeptide rather BD


Chemical Reviews

Review

Table 27. AMPs from Rana Frogs source

name

sequence

R. amurensis

ref 585

ranatuerin-2AMa temporin-1AM

GLLSVFKGVLKGVGKNVAGSLLDQLKCKISGGC FLPLVGKILSGLIGK-NH2

brevinin-1AVa brevinin-1AVb ranatuerin-2AVa ranatuerin-2AVb

FLPLLAASFACTVTKKC FVPLLVSKLVCVVTKKC GLLDVVKGAAKNLLASALDKLKCKVTGC GLMDMVKGAAKNLFASALDTLKCKITGC

brevinin-1AUa brevinin-1AUb ranatuerin-2AUa temporin 1AUa

FLPILAGLAAKLVPKVFCSITKKC FLPILAGLAANILPKVFCSITKKC GILSSFKGVAKGVAKNLAGKLLDELKCKITGC FLPIIGQLLSGLL-NH2

brevinin-1BLa brevinin-1BLb brevinin-1BLc brevinin-1BLd

FLPIIAGIAAKFLPKIFCTISKKC FLPIIAGMAAKVLLKIFCAISKKC FFPIVAGMAGQVLKKIFCTISKKC FFPIVAGVAGQVLKKIYCTISKKC

brevinin-1 brevinin-2

FLPVLAGIAAKVVPALFCKITKKC GLLDSLKGFAATAGKGVLQSLLSTASCKLAKTC

brevinin-1BYa brevinin-1BYb brevinin-1BYc ranatuerin-2BYa ranatuerin-2BYb temporin-1Bya

FLPILASLAAKFGPKLFCLVTKKC FLPILASLAAKLGPKLFCLVTKKC FLPILASLAATLGPKLLCLITKKC GILSTFKGLAKGVAKDLAGNLLDKFKCKITGC GIMDSVKGLAKNLAGKLLDSLKCKITGC FLPIIAKVLSGLL-NH2

brevinin-1CSa ranatuerin-2CSa temporin-1CSa temporin-1CSb temporin-1CSc temporin-1CSd

FLPILAGLAAKIVPKLFCLATKKC GILSSFKGVAKGVAKDLAGKLLETLKCKITGC FLPIVGKLLSGLL-NH2 FLPIIGKLLSGLL-NH2 FLPLVTGLLSGLL-NH2 NFLGTLVNLAKKIL-NH2

brevinin-1CEb chensinin-1 chensinin-2 chensinin-3 temporin-1CEa temporin-1CEb palustrin-2CE temporin-1CEf temporin-1CEg temporin-1CEd temporin-1CEe brevinin-2CE palustrin-2CE chensinin-1CEa chensinin-1CEb chensinin-1CEc chensinin-2CE chensinin-3CE chensinin-4CE brevinin-1CDYa japonicin-1CDYa temporin-CDYb D-1CDYa brevinin-1CDYb brevinin-1CDYc

FLIGMTQGLICLITRKC SAVGRHGRRFGLRKHRKH IIPLPLGYFAKKT GLFSVVKGVLKGVGKNVAGSLLEQLKCKISGGC FVDLKKIANIINSIFGK-NH2 ILPILAPLIGGLLGK-NH2 GLWDSIKNFGKTIALNVMDKIKCKGGGCPP ILPILGKILSTILGK-NH2 ILPIFSWIGHLFGK-NH2 ILPLIASLIGGLLGK-NH2 ILPIIGKILSTIFGK-NH2 GLLSVFKGVLKTAGKNVAKNVAGSLLDQLKCKISGGC GLWDSIKNFGKTIALNVMDKIKCKIGGGCPP LALERRDGWLRLFGLFGLKTRRKH LALERRSGWLRLFGLFGLKPRRKH LALERRDGWLRLFGLFGLKPRRKH IIALPLGYFSK NFAEIFAAVNKLIKQGVVKG LPLRFHGRFRLRTHKKL LLSLALAALPKLFCLIFKKC FFPLALLCKVFKKC ILPILAPLIGGLL-NH2 IIPLPLGYFAKKT FLSLALAALPKLFCLIFKKC FLSLALAALPKFLCLVFKKC

R. arvalis

586, 587

R. aurora aurora

588

R. biairi

589

R. brevipoda

590

R. boylii

591, 592

R. cascadae

593

R. chensinensis

580, 584, 594−597

BE


Chemical Reviews

Review


name

sequence

brevinin-1CDYd brevinin-2CDYa brevinin-2CDYb temporin-CDYa temporin-CDYc temporin-CDYd

FLPLLLAGLPKLLCFLFKKC GLFSVVKGVLKAVGKNVAKNVGGSLLEKLKCKISGGC GLFSVVKGVLKGVGKNVAGSLLEKLKCKISGGC VLPLVGNLLNDLL-NH2 ILPILSLIGGLL-NH2 FIGPIISALASLFG-NH2

esculentin-2PRa esculentin-2PRb ranatuerin-2PRa ranatuerin-2PRb ranatuerin-2PRc ranatuerin-2PRd ranatuerin-2PRe brevinin-1PRa brevinin-1PRb brevinin-1PRc brevinin-1PRd temporin-PRa temporin-PRb temporin-PRc

GVFSFLKTGAKLLGSTLLKMAGKAGAEHLACKATNQC GIFSALAAGVKLLGNTLFKMAGKAGAEHLACKATNQC GILDSFKGVAKGVAKDLAGKLLDKLKCKITGC GILDTFKGVAKGVAKDLAVHMLENLKCKMTGC GILDSFKDVAKGVATHLLNMAKCKMTGC GILSSIKGVAKGVAKNVAAQLLDTLKCKITGC GIMNTVKDVATGVATHLLNMVKCKITGC FLPVLTGLTPSIVPKLVCLLTKKC FLPVLAGLTPSIVPKLVCLLTKKC FFPMLAGVAARVVPKVICLITKKC FLPMLAGLAASMVPKLVCLITKKC FLPILGNLLSGLL-NH2 FLPIITNLLGKLL-NH2 NFLDTLINLAKKFI-NH2

brevinin-1DRa brevinin-1DRb brevinin-1DRc brevinin-1DRd ranatuerin-2DRa ranatuerin-2DRb RV-23 temporin-1DRa temporin-1DRb temporin-1DRc

FLPILAGLAADMLPKVFCSITKKC FLPILAGLATKIVPKVFCLITKKC FLPILAGLAAKIVPKVFCLVTKKC FLPILAGLAAKIVPKVFCLITKKC GIMDTFKGVAKGVAKDLAVKLLDNFKCKITGC GIMDTFKGIAKGVAKNLAGKLLDELKCKMTGC RIGVLLARLPKLFSLFKLMGKKV HFLGTLVNLAKKIL-NH2 NFLGTLVNLAKKIL-NH2 FLPIIASVLSSLL-NH2

brevinin-1CDYa brevinin-1CDYd brevinin-1DYa brevinin-1DYb brevinin-1DYc brevinin-1DYd brevinin-1DYe brevinin-2CDYa brevinin-2CDYb brevinin-2DYa brevinin-2DYb brevinin-2DYc brevinin-2DYd dybowskin-1CDYa dybowskin-2CDYa dybowskin-2CDYb japonicin-1CDYa temperin-CDYa temperin-CDYb temperin-CDYd temperin-CDYe temperin-1DYa dybowskin-4 dybowskin-6 temperin-YJa dybowskin-YJa ranatuerin-2YJ dybowskin-YJb

LLSLALAALPKLFCLIFKKC FLPLLLAGLPKLLCFLFKKC FLSLALAALPKFLCLVFKKC FLSLALAALPKLFCLIFKKC FLPLLLAGLPKLLCLFFKKC FLIGMTHGLICLISRKC FLIGMTQGLICLITRKC GLFSVVTGVLKAVGKNVAKNVGGSLLEQLKCKISGGC GLFSVVTGVLKAVGKNVAGSLLEQLKCKISGGC GLLSAVKGVLKGAGKNVAGSLMDKLKCKLFGGC GLFDVVKGVLKGAGKNVAGSLLEQLKCKLSGGC GLFDVVKGVLKGVGKNVAGSLLEQLKCKLSGGC GIFDVVKGVLKGVGKNVAGSLLEQLKCKLSGGC IIPLPLGYFAKKT SAVGRHGRRFGLRKHRKH SAVGRHSRRFGLRKHRKH FFPLALLCKVFKKC VLPLVGNLLNDLLGK-NH2 ILPILAPLIGGLLGK-NH2 FIGPLISALASLFKG-NH2 FIGPIISALASLFGG-NH2 FIGPIISALASLFG-NH2 VWPLGLVICKALKIC FLPLLLAGLPLKLCFLFKKC VLPLLETCSMTCWENNQTFGK-NH2 IIPLPLGYFAKKKKKKDPVPLDQ GLMDIFKVAVNKLLAAGMNKPRCKAAHC IIPLPLGYFAKKP

R. pretiosa

ref

417

R. draytonii

598

R. dybowskii

581, 582, 599, 600

BF


Chemical Reviews

Review


name

sequence

R. esculenta

ref 572, 601, 602

brevinin-1E brevinin-1Ea brevinin-1Eb brevinin-1Ec brevinin-2EA brevinin-2EB brevinin-2EC brevinin-2ED esculentin-1c esculentin-1A esculentin-1B esculentin-2A esculentin-2B ranacyclin-E ranacyclin-T temporin 1Ec

FLPLLAGLAANFLPKIFCKITRKC FLPAIFRMAAKVVPTIICSITKKC VIPFVASVAAEMQHVYCAASRKC FLPLLAGLAANFFPKIFCKITRKC GILDTLKNLAISAAKGAAQGLVNKASCKLSGQC GILDTLKNLAKTAGKGALQGLVKMASCKLSGQC GILLDKLKNFAKTAGKGVLQSLLNTASCKLSGQC GILDSLKNLAKNAGQILLNKASCKLSGQC GIFSKLGRKKIKNLLISGLKNVGKEVGMDVVRTGIDIAGCKIKGEC GIFSKLAGKKIKNLLISGLKNVGKEVGMDVVRTGIDIAGCKIKGEC GIFSKLAGKKLKNLLISGLKNVGKEVGMDVVRTGIDIAGCKIKGEC GILSLVKGVAKLAGKGLAKEGGKFGLELIACKIAKQC GIFSLVKGAAKLAGKGLAKEGGKFGLELIACKIAKQC SAPRGCWTKSYPPKPCK GALRGCWTKSYPPKPCK-NH2 FLPVIAGLLSKLF-NH2

brevinin-1HSa brevinin-1HSb brevinin-2HSa brevinin-2HSb esculentin-1HSa esculentin-2HSa nigrocin-2HSa nigrocin-2HSb

FLPAVLRVAAKIVPTVFCAISKKC FLPAVLRVAAQVVPTVFCAISKKC GLLDSLKNLAINAAKGAGQSVLNTLSCKLSKTC GLLDTLKNMAINAAKGAGQSVLNTLSCKLSKTC GIFSKFGGKAIKNLFIKGAKNIGKEVGMDVIRTGIDVAGCKIKGEC GIFSLIKGAAQLIGKTVAKEAGKTGLELMACKVTKQC GLLGSLFGAGKKVACALSGLC GLLGSIFGAGKKIACALSGLC

brevinin-1CDYc

FLSLALAALPKFLCLVFKKC

japonicin-1Ja japonicin-2Ja temporin-1Ja brevinin-1Ja

FFPIGVFCKIFKTC FGLPMLSILPKALCILLKRKC ILPLVGNLLNDLL-NH2 FLGSLIGAAIPAIKQLLGLKK-NH2

brevinin-1La brevinin-1Lb esculentin-2L ranatuerin-2La ranatuerin-2Lb temporin-1La temporin-1Lb temporin-1Lc

FLPMLAGLAASMVPKLVCLITKKC FLPMLAGLAASMVPKFVCLITKKC GILSLFTGGIKALGKTLFKMAGKAGAEHLACKATNQC GILDSFKGVAKGVAKDLAGKLLDKLKCKITGC GILSSIKGVAKGVAKNVAAQLLDTLKCKITGC VLPLISMALGKLL-NH2 NFLGTLINLAKKIM-NH2 FLPILINLIHKGLL-NH2

ranatuerin-2Ma ranatuerin-2Mb temporin 1M

GLLSFKGVAKGVAKDLAGKLLEKLKCKITGC GIMDSKGVAKNLAAKLLEKLKCKITGC FLPIVGKLLSGLL-NH2

nigrocin-1 nigrocin-2 temporin-1RNa temporin-1RNb brevinin-2RNa

GLLDSIKGMAISAGKGALQNLLKVASCKLDKT GLLSKVLGVGKKVLCGVSGLC ILPIRSLIKKLL-NH2 FLPLKKLRFGLL-NH2 GLFDVVKGVLKGVGKNVAGSLLEQLKCKLSGGC

shuchin shuchin shuchin shuchin shuchin

NALSMPRNKCNRALMCFG NALSSPRNKCDRASSCFG KAYSMPRCKGGFRAVMCWL-NH2 KAYSTPRCKGLFRALMCWL-NH2 KAYSMPRCKYLFRAVLCWL-NH2

R. hosil

415

R. huanrenensis

581

R. japonica

560, 603, 604

R. luteiventris

541

R. muscosa

605

R. nigromaculata

606, 607

R. shuchinae

583, 608 1 2 3 4 5

R. tagoi okiensis

19 brevinin-1TOa brevinin-1TOb

GIGSILGVIAKGLPTLISWIKNRG-NH2 VIGSILGVIAKGLPTLISWIKNRG-NH2 BG


Chemical Reviews

Review


name

sequence

temporin-TOa temporin-TOb ranatuerin-2TOa ranatuerin-2TOb ranatuerin-2TOc ranatuerin-2TOd DK-25 DF22-amide

FLPILGKLLSGFLGK-NH2 FLPILGKLLSGLLGK-NH2 GLLNVIKDTAQNLFAAALDKLKCKVTKCN GLLNVIKDTAQNLFAAALFKLKCKVTKCN GLLNVIRDTAQNLFAAALEKLKCKVIKCN GLLNVIKDTAQNLFTAALEKLKCKVIKCN DVNDLKNLCAKTHNLLPMCAMFGKK DVNDLKNLCAKTHNLLPMCAMF-NH2

ranatuerin-2OK brevinin-1OKa brevinin-1OKb brevinin-1OKc brevinin-1OKd

SFLNFFKGAAKNLLAAGLDKLKCKISGTQC FFGSMIGALAKGLPSLSLISLIKK-NH2 FFPFVINELAKLPSLISLLKK-NH2 FFGSIIGALAKGLPSLISLISLISLIKK-NH2 FLGSIIGALAKGLPSLIALIKK-NH2

brevinin-2Oa brevinin-2Ob temporin-1Oa temporin-1Ob temporin-1Oc temporin-1Od temporin-1Oe temporin-1Of temporin-1Og ranatuerin-2Oa ranatuerin-2Ob ranatuerin-2Oc ranatuerin-2Od palustrin-2Oa

GLFNVFKGLKTAGKHVAGSLLNQLKCKVSGGC GIFNVFKGALKTAGKHVAGSLLNQLKCKVSGEC FLPLLASLFSRLL-NH2 FLPLIGKILGTIL-NH2 FLPLLASLFSRLF-NH2 FLPLLASLFSGLF-NH2 ILPLLGNLLNGLL-NH2 SLILKGLASIAKLF-NH2 FLSSLLSKVVSLFT-NH2 GLMDILRGAGKNLIATGLNALRCKITKC GLLDILRGAGKNLIATGLNTLRCKLTKC GLLDVLKGAAKNLIATGLNALSCKFTKC GLLDTLKGAAKDLIATGLNALRCKLTKC GLWDNIKNFGKTFALNAIEKLKCKITGGCPP

brevinin-1PLa brevinin-1PLb brevinin-1PLc esculentin-1PLa esculentin-1PLb esculentin-2PLa nigrocin-2P palustrin-1a palustrin-1b palustrin-1c palustrin-1d palustrin-2a palustrin-2b palustrin-2c palustrin-3a palustrin-3b ranatuerin-2PLa ranatuerin-2PLb ranatuerin-2PLc ranatuerin-2PLd ranatuerin-2PLe ranatuerin-2PLf temporin-1PLa

FFPNVASVPGQVLLKKIFCAISKKC FLPLIAGLAANFLPKIFCAITKKC FLPVIAGVAAKFLPKIFCAITKKC GLFPKINKKKAKTGVFNIIKTVGKEAGMDLIRTGIDTIGCKIKGEC GIFTKINKKKAKTGVFNIIKTIGKEAGMDVIRAGIDTISCKIKGEC GLFSILKGVGKIALKGLAKNMGKMGLDLVSCKISKEC GLLSKVLGVGKKVLCGVSGLC ALFSILRGLKKLGKMGQAFVNCEIYKKC ALFSILRGLKKLGNMGQAFVNCKIYKKC ALSILRGLEKLAKMGIALTNCKATKKC ALSILKGLEKLAKMGIALTNCKATKKC GFLSTVKNLATNVAGTVLDTIRCKVTGGCRP GFFSTVKNLATNVAGTVIDTLKCKVTGGCRS GFLSTVKNLATNVAGTVIDTLKCKVTGGCRS GIFPKIIGKGIKTGIVNGIKSLVKGVGMKVFKAGLNNIGNTGCNEDEC GIFPKIIGKGIKTGIVNGIKSLVKGVGMKVFKAGLSNIGNTGCNEDEC GIMDTVKNVAKNLAGQLLDKLKCKITAC GIMDTVKNAAKDLAGQLLDKLKCRITGC GLLDTIKNTAKNLAVGLLDKIKCKMTGC GIMDSVKNVAKNIAGQLLDKLKCKITGC GIMDSVKNAAKNLAGQLLDTIKCKITAC GIMDTVKNAAKDLAGQLDKLKCRITGC FLPLVGKILSGLI-NH2

brevinin-2PRa brevinin-2PRb brevinin-2PRc brevinin-2PRd brevinin-2PRe ranatuerin-2PRa temporin 1Pra

GLMSLFKGVLKTAGKHIFKNVGGSLLDQAKCKITGEC GLMSLFRGVLKTAGKHIFKNVGGSLLDQAKCKITGEC GLMSVTKGVLKTAGKHIFKNVGGSLLDQAKCKISGQC GLMSVLKGVLKTAGKHIFKNVGGSLLDQAKCKITGQC GLLSVLKGVLKTTGKHIFKNVGGSLLDQAKCKISGQC GLMDVFKGAAKNLLASALDKIRCKVTKC ILPILGNLLNGLL-NH2

R. okinavana

ref

561

R. ornativentris

609, 610

R. palustris

25, 589, 611

R. pirica

612

BH


Chemical Reviews

Review


name

sequence

temporin-1PRb

ILPILGNLLNSLL-NH2

lividin-RP pleurain-a1 pleurain-a2 pleurain-a3 pleurain-a4 pleurain-B1 pleurain-B2 pleurain-B3 pleurain-B4 pleurain-B5 pleurain-C1 pleurain-C2 pleurain-D1 pleurain-D2 pleurain-D3 pleurain-D4 pleurain-D5 pleurain-D6 pleurain-E pleurain-G1 pleurain-G2 pleurain-G3 pleurain-G4 pleurain-G5 pleurain-G6 pleurain-G7 pleurain-J1 pleurain-J2 pleurain-K pleurain-M1 pleurain-M2 pleurain-N pleurain-P

SFLCDLKILATNAAKNAGQCVVTTLSCKLCGTC SIITMTKEAKLPQLWKQIACRLYNTC SIITMTKEAKLPQSWKQIACRLYNTC SIITMTREAKLPQLWKQIACRLYNTC SIITTTKEAKLPQLWKQIACRLYNTC FLGGLLASLLGKIGKK FLGGLLSGIFKHLGKK FLGGLLFGIFKHLGKK FLGGLLSGIFKHLGKK FLGGLLSSIFGHLGK YPELQQDLIARLLGK FPELQQDLIARLLGK FLSGILKLAFKIPSVLCAVLKNC FLSGILKLASKIPSVLCAVLKNC FFSGILKLVFKIPSVLCAVLKNC FRSGILKLASKIPSVLCAVLKNC FFSGILKLVFKIPSVLCAVLKIVET FLSGILKLASKIPSVLCAVLKKLLKLKLEII AKAWGIPPHVIPQIVPVRIRPLCGNV GFWDSVKEGLKNAAVTILNKIKCKISECPPA GLWDSVKEGLKNAAVTILNKIKCKIFECPPA GLWDSVKEGLKNAAVTILNKIKCKISECPPA GLWDSVKEGFKNAAVTLLNKIKCKISACPPA GIFDSIKEGFKNAAVTLLDKIKCKISACPPA GIFDSIKEGFKNAAVTLLNKIKCKISDCPPA GIFDSIKEGFKNAAVTLLNKIKCKISECPPA FIPGLRRLFATVVPTVVCAINKLPPG FIPGLRRLSATVVPTVVCAINKLPPG MLKWKNDFFQEF GLLDSVKEGLKKVAGQLLDTLKCKISGCTPA GLLDSVKEGLKKAAGQLLDTLKCEISGCTPA GFFDRIKALTKNVTLELLNTITCKLPVTPP SFGAKNAVKNGLQKLRNQCQANNYQGPFCDIFKKNP

brevinin-1E brevinin-1Ecb brevinin-1R brevinin-1Ra brevinin-2Ec brevinin-2Ef brevinin-2Eg brevinin-2Ej brevinin-2Ra brevinin-2Rb brevinin-2Rc brevinin-2Rd esculentin-1a/b esculentin-1R esculentin-2R esculentin-2Ra esculentin-2Rb ranatuerin-2R ranatuerin-2Ra

FLPLLAGLAANFLPKIFCKITRKC FLPLLAGLAANFFPKIFCKITRKC FFPAIFRLVAKVVPSIICSVTKKC VIPFVASVAAEMMQHVYCAASRRC GILLDKLKNFAKTAGKGVLQSLLNTASCKLSGQC GIMDTLKNLAKTAGKGALQSLVKMASCKLSGQC GIMDTLKNLAKTAGKGALQSLLNHASCKLSGQC GIFLDKLKNFAKGVAQSLLNKASCKLSGQC GILDSLKNFAKDAAGILLKKASCKLSGQC GLMSTLKGAATNAAVTLLNKLQCKLTGTC GLMSTLKGAATNVAVTLLNKLQCKLTGTC GILDSLKNLAKNAAQILLNKASCKLSGQC LKNVGKEVGMDVVRTGIDIAGCKIKGEC GIFSKLAGKKLKNLLISGLKSVGKEVGMDVVRTGIDIAGCKIKGEC GILSLVKVAKLAGKTFAKEGGKFGLEFIACKVTNQC GILSLVKGAAKLLGKGLAKEGGKVGLEFIACKVTNQC GIFSLVKGVAKLAGKTLAKEGGKFGLELAMCKIAKQC AVNIPFKVKFRCKAAFC AAKLLLNPKFRCKAAFC

gaegurin-1 gaegurin-2 gaegurin-3 gaegurin-4 gaegurin-5

SLFSLIKAGAKFLGKNLLKQGACYAACKASKQC GIMSIVKDVAKNAAKEAAKGALSTLSCKLAKTC GIMSIVKDVAKTAAKEAAKGALSTLSCKLAKTC GILDTLKQFAKGVGKDLVKGAAQGVLSTVSCKLAKTC FLGALFKVASKVLPSVFCAITKKC

R. pleuraden

ref 272, 573

R. ridibunda

587, 613

R. rugosa

566, 614, 615

BI


Chemical Reviews

Review


name

sequence

gaegurin-6 rugosin A rugosin B rugosin C

FLPLLAGLAANFLPTIICKISYKC GLLNTFKDWAISIAKGAGKGVLTTLSCKLDKSC SLFSLIKAGAKFLGKNLLKQGAQYAACKVSKEC GILDSFKQFAKGVGKDLIKGAAQGVLSTMSCKLAKTC

brevinin-1E brevinin-2Ec esculentin-1 esculentin-1B

FLPLLAGLAANFLPKIFCKITRKC GILLDKLKNFAKTAGKGVLQSLLNTASCKLSGQC GIFSKFGRKKIKNLLISGLKNVGKEVGMDVVRTGIDIAGCKIKGEC GIFSKLAGKKLKNLLISGLKNVGKEVGMDVVRTGIDIAGCKIKGEC

melittin-related peptide temporin-1SKa temporin-1SKb temporin-1SKc temporin-1SKd brevinin-2SKa brevinin-2SKb ranatuerin-2

VIGSILGALASGLPTLISWIKNR-NH2 FLPVILPVIGKLLNGIL-NH2 FLPVILPVIGKLLSGIL-NH2 AVDLAKIANIAN KVLSSLF-NH2 FLPMLAKLLSGFL-NH2 GLFSAFKKVGKNVLKNVAGSLMDNLKCKVSGEC GLFNVFKKVGKNVLKNVAGSLMDNLKCKVSGEC GLLDAIKDTAQNLFANVLDKIKCKFTKC

cancrin

GSAQPYKQLHKVVNWDPYG

brevinin-1Da

ILPLLLGKVVCAITKKC

brevinin-1SE esculentin-1SEa esculentin-1SEb esculentin-2SE ranatuerin-2SEa ranatuerin-2SEb ranatuerin-2SEc

FLPLVRGAAKLIPSVVCAISKRC GLFSKFNKKKIKSGLIKIIKTAGKEAGLEALRTGIDVIGCKIKGEC GLFSKFNKKKIKSGLFKIIKTAGKEAGLEALRTGIDVIGCKIKGEC GFFSLIKGVAKIATKGLAKNLGKMGLDLVGCKISKEC GFISTVKNLATNVAGTVIDTIKCKVTGGC AIMDTIKDTAKTVAVGLLNKLKCKITGC GIMDTIKDTAKTVAVGLLNKLKCKITGC

melittin-related peptide temporin-1TGa temporin-1TGc

AIGSILGALAKGLPTLISWIKNR-NH2 FLPILGKLLSGIL-NH2 FLPVILPVIGKLLSGIL-NH2

brevinin-1T brevinin-1Ta brevinin-2T brevinin-2Ta brevinin-2Tb brevinin-2Tc brevinin-2Td melittin-like peptide ranacyclin T temporin-A temporin-B temporin-C temporin-D temporin-E temporin-F temporin-G temporin-H temporin-K temporin-L

VNPIILGVLPKFVCLITKKC FITLLLRKFICSITKKC GLLSGLKKVGKHVAKNVAVSLMDSLKCKISGDC GILDTLKNLAKTAGKGILKSLVNTASCKLSGQC GILDTLKHLAKTAGKGALQSLLNHASCKLSGQC GLWETIKNFGKKFTLNILHKLKCKIGGGC GLWETIKNFGKKFTLNILHNLKCKIGGGC FIGSALKVLAGVLPSIVSWVKQ GALRGCWTKSYPPKPCKGK FLPLIGRVLSGIL-NH2 LLPIVGNLLKSLLGK-NH2 LLPILGNLLNGLL-NH2 LLPIVGNLLNSLL-NH2 VLPIIGNLLNSLL-NH2 FLPLIGKVLSGIL-NH2 FFPVIGRILNGILGK-NH2 LSPNLLKSLLGK-NH2 LLPNLLKSLL-NH2 FVQWFSKFLGRIL-NH2

brevinin-2TSa brevinin-1TSa temporin-1TSa temporin-1TSb temporin-1TSc temporin-1TSd

GIMSLFKGVLKTAGKHVAGSLVDQLKCKITGGC FLGSIVGALASALPSLISKIRN-NH2 FLGALAKIISGIF-NH2 FLPLLGNLLNGLL-NH2 FLPLLGNLLRGLL-NH2 FLPLLASLIGGML-NH2

R. saharica

ref

285

R. sakuraii

41, 563, 592

R. cancrivora

616

R. dalmatina

617

R. sevosa

300

R. tagoi

592, 618

R. temporaria

294, 619, 620

R. tsushimensis

621

BJ


Chemical Reviews

Review


name

sequence

R. zhenhaiensis

ref 622

brevinin-1ZHa brevinin-1ZHb brevinin-1ZHc brevinin-1ZHd brevinin-2ZHa ranatuerin-2ZHa chensinin-1ZHa chensinin-1ZHa

FLPFLLSALPKVFCFFSKKC FLPLLLSALPSFLCLVFKKC FLPLLPSALPSFLCLVFKKC FLPLLLSALPSFSCLVFKKC GIMRVFKGVLKTAGKSVAKNVAGSFLDRLKCKISGGC GLADYWRTAFRANFANLGPGIRCKSARC LALKSGGWLRLFGLKDKKH LALESGGWLRLFGLKDKKH

japonicin-2CHa japonicin-2CHb japonicin-2CHc japonicin-2CHd

FVLPLLGILPKELCIVLKKNC VVPAFVLLKKAICIMLKRNC VVPAFVLLRKAICIMLKRNC VVPAFVLLKKAICIMFKRNC

R. chaochiaoensis Liu

623

In addition, AMPs of O. versabilis are highly homologous to AMPs from North American ranid frogs but not other odorous frogs. Each of the eight AMPs from the skin secretions of O. versabilis is identical to the corresponding peptide families from R. palustris. In addition, the primary structures of two ranatuerins are similar to ranatuerin 2B and ranatuerin 2P from the closely related L. berlandieri and L. pipiens, respectively.551 Different structures of AMPs from odorous frogs lead to markedly different antimicrobial activities. Palustrin-2ISa and palustrin-2ISc and members of the esculentin-1, esculentin-2, brevinin-2, and nigrocin-2 families from O. ishikawae have broad-spectrum growth inhibitory activities against E. coli, S. aureus, B. subtilis, and C. albicans.550 Palustrin-2ISd and odorranain-MISa from O. ishikawae have some antimicrobial activity. Brevinin-1ISa strongly inhibits Gram-positive bacteria and the fungus but shows no effects against E. coli. However, all ishikawains inhibit E. coli growth.550 In contrast to most temporin peptides that have antimicrobial activity against only Gram-positive bacteria, temporin-HN1 and temporin-HN2 have potent broad-spectrum antimicrobial activity. In addition, they have low hemolytic activity simlar to other temporins. The nigrocin-2-related peptides from O. grahami, nigrocin-2LVa, nigrocin-2LVb, nigrocin-2SCa, nigrocin-2SCb, nigrocin-2SCc, nigrocin-2VB, and nigrocin-2HJ have relatively weak activity against Gram-negative and Grampositive bacteria.309,546,548 2.14.26. Rana. An extraordinary number of AMPs have been identified from frogs in the genus Rana, which contains 48 species in Eurasia and North America.559 These AMPs belong to at least 13 well-established AMP families: brevinin-1, brevinin-2, esculentin-1, esculentin-2, gaegurin, japonicin-1, japonicin-2, palustrin-2, ranacyclin, ranatuerin-1, ranatuerin-2, tigerinin, and temporin. In general, a peptide family consisting of a group of peptides with common structural characteristics exists in more than one Rana species, and the AMPs in one species are also in more than one family (Table 27). The majority of Rana AMPs contain a disulfide bond at the C-terminus of the peptide that forms a ring, and most members of the brevinin-1, brevinin-2, esculentin-1, esculentin-2, japonicin-1, ranatuerin-1, palustrin-2, and gaegurin families contain a 7-aa ring, the “rana box”, at the C-terminus. Peptides of the ranatuerin-2, japonicin-2, tigerinin, and ranacyclin families contain rings of 6, 8, 9, and 11 residues, respectively. Nigroain-D has a 13-residue ring in a disulfide bond of two C

residues at the N-terminus, and nigroain-E has the same loop in the middle of its sequence.4 Several members of brevinin-1 family are acyclic and contain deletions. Brevinin-1Ja from R. japonica and four structurally related brevinin-1Ok peptides from R. okinavana lack the C18 in the brevinin-1 consensus sequence and therefore lack the cyclic domain. Furthermore, their C24 residues have mutated to a G that is a substrate for peptidyl-glycine α-amidating monooxygenase, resulting in C-terminal residue α-amidation.560,561 Brevinin-1Ok peptides have potent antimicrobial activities against E. coli and S. aureus, confirming that a cyclic domain is not essential for antimicrobial activity. However, cyclic esculentin 1 kills bacteria more rapidly than a linear version.561,562 Thus, the function of the disulfide ring is unknown. Ranalexins from secretions of bullfrogs in the Aquarana group show strong sequence identity to members of the brevinin-1 family but have four residues deleted, leading to loss of the ring structure.529 Similarly, the melittin-related peptides identified in the skins of R. draytonii, R. sakuraii, and R. tagoi also lack a ring structure.563 Some ring-containing Rana AMPs are mostly unstructured in water but display marked secondary structure in either trifluoroethanol or model micelles. For example, brevinin-1E, gaegurin-4, gaegurin-6, and esculentin-1c have 2−3 helixes separated by a flexible hinge in lipid membranes or membranemimetic environments.564−568 Gaegurin-4 contains 2 α-helixes separated by a flexible loop between K11 and K15. The first helix spans I2 to A10, and the second helix consists of residues between D16 and K32 followed by a disulfide ring. This special structure makes gaegurin-4 form voltage-dependent pores in lipid bilayers. However, the removal of the C-terminal disulfide does not substantially change the structure of gaegurin-4 in the membrane, indicating that it is unimportant in inducing pore formation and antimicrobial activity.569,570 However, the antimicrobial specificity might be affected mainly by electrostatic interactions of the disulfide region with phospholipids.571 The disulfide bond of gaegurin-6 might stabilize the formation of an α-helical structure in lipid membranes that correlates with antimicrobial activity.567 Each of three α-helices of esculentin1c displays amphipathic features and is important for this peptide to permeate bacterial membranes for antimicrobial activity.568 However, unlike most AMPs from Rana frog skins, pLR, ranacyclin-E, and ranacyclin-T adopt a mainly random coil conformation even in a membrane-mimetic solvent such as 1% SDS. Ranacyclins predominantly interact with the hydrophobic BK


Chemical Reviews

Review

Table 28. Antivirus Peptides from Amphibians name

sequence

caerin 1.1 caerin 1.9 maculatin 1.1 aurein 1.2 aurein 1.2 syn ranatuerin 9 D74 D76 buforin II pseudin 1 D88 brevinin-2 related maculatin 1.3 ascaphin-8 desertcolin 1 D98 PGLa

GLLSVLGSVAKHVLPHVVPVIAEHL-NH2 GLFGVLGSIAKHVLPHVVPVIAEKL-NH2 GLFGVLAKVAAHVVPAIAEHF-NH2 GLFDIIKKIAESF-NH2 GLFDIIEKIAKSW-NH2 FLFPLITSFLSKVL IKWKKLLRAAKRIL-NH2 FFGKVLKLIRKIF-NH2 TRSSRAGLQFPVGRVHRLLRK GLNTLKKVFQGLHEAIKLINNHVQ NLVSGLIEARKYLEQLHRKLKNRKV GIWDTIKSMGKVFAGKILQNL-NH2 GLLGLLGSVVSHVVPAIVGHF-NH2 GFKDLLKGAAKALVKTVLF-NH2 GLADFLNKAVGKVVDFVKS-NH2 SLSRFLRFLKIVYRRAF-NH2 GMASKAGAIAGKIAKVALKAL-NH2

dermaseptin S1

ALWKTMLKKLGTMALHAGKAALGAAADTISQGTQ

dermaseptin S2

ALWFTMLKKLGTMALHAGKAALGAAANTISQGTQ

dermaseptin S3

ALWKDVLKKIGTVALHAGKAAFGAAADTISQG

dermaseptin S4

ALWMTLLKKVLKAAAKALNAVLVGANA

dermaseptin S5 ranatuerin-2P

GLWSKIKTAGKSVAKAAAKAAVKAVTNAV GLMDTVKNVAKNLAGHMLDKLKCKITGC

esculentin-2P

GFLSIFRGVAKFASKGLGKDLARLGVNLVACKISKQC

temporin A

FLPLIGRVLSGIL-NH2

magainin II brevinin-1

GIGKFLHSAKKFGKAFVGEIMNS FLPVLAGIAAKVVPALFCKITKKC

virus/MIC or IC50 or EC50

ref

HIV/7.8 μM (IC50) HIV/1.2 μM (IC50) HIV/11.3 μM (IC50) HIV/11.7 μM (IC50) HIV/10.5 μM (IC50) HIV/16.7 μM (EC50) HIV/1.3 μM (IC50) HIV/0.63 μM (EC50) HIV/>41.1 μM (EC50) HIV/35.7 μM (EC50) HIV/>33.3 μM (EC50) HIV/1.65 μM (EC50) HIV/4.0 μM (EC50) HIV/1.2 μM (EC50) HIV/>49.9 μM (EC50) HIV/0.83 μM (EC50) HIV/>50.8 μM (EC50) CCV/100 μM (IC50) FV3/12 μM (IC50) CCV/3 μM (IC50) HSV-1/32 μg/mL (MIC)

624 624 624 625 625 625 625 625 625 625 625 625 625 625 625 625 625 628 628 628 627

HSV-1/16 μg/mL (MIC)

627

HSV-1/8 mg/mL (MIC) HSV-1/2 μg/mL (MIC) HIV/2 μM (IC50) HSV-1/without effect FV3/>5 μM (IC50) CCV/>5 μM (IC50)

627 627 628 627 629 629

FV3/

The Chemistry and Biological Activities of Peptides from Amphibian

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