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Conservation and Diversity in the Primary Forward Photodynamics of Red/Green Cyanobacteriochromes Delmar S. Larsen Biochemistry, Just Accepted Manuscript • Publication Date (Web): 29 Dec 2014 Downloaded from http://pubs.acs.org on December 30, 2014
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Conservation and Diversity in the Primary Forward Photodynamics of Red/Green Cyanobacteriochromes
Journal: Manuscript ID: Manuscript Type: Date Submitted by the Author: Complete List of Authors:
Biochemistry bi-2014-012755.R1 Article 23-Dec-2014 Gottlieb, Sean; University of California, Davis, Chemistry Kim, Peter; University of California, Davis, Chemistry Chang, Che-Wei; University of California, Chemistry Hanke, Samuel; University of California, Chemistry Hayer, Randeep; UC Davis, Chemistry Rockwell, Nathan; University of California, Molecular and Cellular Biology Martin, Shelley; University of California, Davis, Molecular and Cellular Biology Lagarias, J. Clark; University of California, Molecular and Cellular Biology Larsen, Delmar; University of California, Davis , Department of Chemistry
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Biochemistry
Monday, December 29, 2014
Conservation and Diversity in the Primary Forward Photodynamics of Red/Green Cyanobacteriochromes
Sean M. Gottlieb1, Peter W. Kim1, Che-Wei Chang1, Samuel J. Hanke1, Randeep J. Hayer1, Nathan C. Rockwell2, Shelley S. Martin2, J. Clark Lagarias2, Delmar S. Larsen1* 1
Department of Chemistry University of California, Davis One Shields Ave, Davis, 95616 2
Department of Molecular and Cell Biology University of California, Davis One Shields Ave, Davis, CA, 95616
Running title: Primary Photodynamics of Red/Green Cyanobacteriochromes
† This work was supported by a grant from the Chemical Sciences, Geosciences, and Biosciences Division, Office of Basic Energy Sciences, Office of Science, United States Department of Energy (DOE DE-FG02-09ER16117) to both J.C.L. and D.S.L.
* Corresponding Author: Delmar S. Larsen, Department of Chemistry, University of California, Davis, Davis CA 95616. Telephone: (530) 754-9075; E-mail:
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Monday, December 29, 2014 1
Abbreviations used in this paper: CBCR, cyanobacteriochrome; CBD, chitin-binding domain;
CD, circular dichroism; EADS, evolution-associated difference spectrum; SADS, speciesassociated difference spectra; ESI, excited-state intermediate; ESA, excited-state absorption; SE, stimulated emission; GAF, domain name derived from cGMP phosphodiesterase/adenylyl cyclase/FhlA; GSA, ground-state absorbance; NOPA, non-collinear optical parametric amplifier; PAS, (Per-ARNT-Sim); PΦB, phytochromobilin; PCB, phycocyanobilin; Pr, red-absorbing ground state of red/far-red phytochromes; Pfr, far-red-absorbing photoproduct state of red/far-red phytochromes;
15Z
Pr, red-absorbing ground state of red/green CBCRs;
15E
Pg, green-absorbing
photoproduct state of red/green CBCRs; Pg*, excited-state population(s) derived from photoexcitation of Pg or
15E
Pg; PYP, photoactive yellow protein; Φ, total photocycle quantum
yield; ΦLumi-Rf, quantum yield of generating Lumi-Rf; Φmeta, quantum yield of generating Meta-R; Φf, fluorescence quantum yield.
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Biochemistry
Monday, December 29, 2014 ABSTRACT Phytochromes are red/far-red photosensory proteins that detect the ratio of red to far-red light. Crucial to light regulation of plant developmental biology, phytochromes are also found in fungi, bacteria, and eukaryotic algae. In addition to phytochromes, cyanobacteria also can contain distantly related cyanobacteriochromes (CBCRs), that like phytochromes utilize the photoisomerization of a linear tetrapyrrole chromophore to convert between two photostates with distinct spectral properties. CBCRs exhibit a wide range of photostates spanning the visible spectraum and even the near ultraviolet. In both phytochromes and CBCRs, biosynthesis initially yields a holoprotein with the bilin in the 15Z configuration, and the 15E photoproduct can often revert to the 15Z photostate in the absence of light (dark reversion). One CBCR subfamily, the red/green CBCRs, typically exhibits red-absorbing dark states and green-absorbing photoproducts. Dark reversion is extremely variable in red/green CBCRs, with known examples ranging from seconds to days. One red/green CBCR, NpR6012g4 from Nostoc punctiforme, is also known to exhibit an unusually high quantum yield of ~40% for forward photoconversion, compared to 10-20% for phytochromes and CBCRs from other subfamilies. In the current study, we use time-resolved pump-probe absorption spectroscopy with broadband detection and multicomponent global analysis to characterize forward photoconversion of seven additional red/green CBCRs from N. punctiforme on the ultrafast timescale. Our results reveal that red/green CBCRs exhibit a conserved pathway for primary forward photoconversion, but there is considerable diversity in excited-state lifetime, photochemical quantum yield, and primary photoproduct stability.
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Monday, December 29, 2014 INTRODUCTION Increasing research effort is directed toward applying photoactive proteins in biological applications such as genetically encoded fluorescent probes and light-regulated control of gene expression (optogenetics).1-3 Such photosensory proteins exploit the excitation of bound chromophores to generate fluorescence or to generate a biochemical signal that can then be transduced to the cell. Photoreceptors are thus important components in the growing biological “tool chest” of photoactive materials.4-6 Although the mechanisms underlying photoinduced responses differ depending on the nature of the specific photoreceptor,7 they typically originate from a small structural change of the chromophore that leads to large-scale structural rearrangements that modulate a biological ‘output’ to interface with biological signal transduction pathways.8 Phytochrome photoreceptors use linear tetrapyrrole (bilin) chromophores to detect red (650-700 nm) and far-red (720-750 nm) light via reversible photoconversion between red- and far-red-absorbing forms (Pr and Pfr, respectively).5, 9 Phytochromes were initially discovered in plants, in which they regulate a wide range of light-induced responses,10,
11
and have
subsequently been found in other photosynthetic organisms, including cyanobacteria, purple photosynthetic bacteria, and glaucophyte, charophyte, prasinophyte, cryptophyte, and heterokont algae.5,
12, 13
Phytochromes have also been found in some nonphotosynthetic bacteria and
filamentous fungi.12, 14, 15 In such nonphotosynthetic organisms, phytochromes use biliverdin IXα (BV) as chromophore, while plant and most cyanobacterial phytochromes typically utilize the more
reduced
phytochromobilin
(PΦB)
and
phycocyanobilin
(PCB)
chromophores,
respectively.16 The primary photoreaction underlying phytochrome activity is an ultrafast (
