AMINO ACID SEQUENCE OF FERREDOXIN
Rexrodt, F. W., Hopper, K. E., Fietzek, P. P., and Kiihn, K. (1973), Eur. J . Biochem. 38, 384. Traub, W., and Piez, K. A. (1971), Advan. Protein Chem. 25, 243. Wendt, P., Fietzek, P. P., and Kuhn, K. (1972a) FEBS (Fed. Eur. Biochem. Soc.) Lett. 26, 69. Wendt, P., von der Mark, K., Rexrodt, F., and Kiihn, K. ( I 972b), Eur. J . Biochem. 30, 169.
Kang, A. H., Bornstein, P., and Piez, K. A. (1967), Biochemistry 6, 788. Miller, E. J., and Piez, K. A.( 1 966), Anal. Biochem. 16, 320. Piez, K. A.,Balian, G., Click, E. M., and Bornstein, P. (1972), Biochem. Biophys. Res. Commun. 48, 990. Rauterberg, J., Fietzek, P., Rexrodt, F. W., Becker, V., Stark, M., and Kiihn, K. (1972), FEBS (Fed. Eur. Biochem. Soc.) Lett. 21. 75.
Amino Acid Sequence of Ferredoxin from a Photosynthetic Green Bacterium, Chlorobium limicolat Masaru Tanaka, Mitsuru Haniu, Kerry T. Yasunobu,* M. C. W . Evans, and Krishna K. Rao
weight of the native ferredoxin was calculated to be 6923. A ABSTRACT: The amino acid sequence of ferredoxin I from the comparison of the sequences was made between Chlorobium photosynthetic green sulfur-reducing bacteria, Chlorobium limicola. was deduced to be: Ala-Leu-Tyr-Ile-Thr-Glu-Glu-limicola ferredoxin and the other ferredoxins which have already been sequenced. The photosynthetic bacterial ferredoxCys-Thr-Tyr-Cys-Gly-Ala-Cys-Glu-Pro-Glu-Cys-Pro-Valins appear to be intermediate in size when compared with the Thr-1Ala-Ile-Ser-Ala-Gly-Asp-Asp-Ile-Tyr-Val-Ile-Asp-Alaclostridial and plant ferredoxins and therefore the sequences of Asn-'Thr-Cys-Asn-Glu-Cys-Ala-Gly-Leu-Asp-Glu-Gln-Alathese ferredoxins are useful for extracting evolutionary data. Cys-Val-Ala-Val-Cys-Pro-Ala-Glu-Cys-Ile-Val-G~n-Gly. The protein consists of 60 amino acid residues and the molecular
T h e amino acid sequences of ferredoxins from seven anaerobic fermentative bacteria (Tanaka et al., 1966, 1971, 1973; Benson et a/., 1967; Tsunoda et al., 1968; Rall et al.. 1969; Travis et al., 1971) are known and these sequences are extremely homologous except for a species from Desulfovibrio gigas (Travis et al., 1971). The amino acid sequence of ferredoxin from the purple sulfur photosynthetic bacterium Chromatium, although 26 amino acids longer than the clostridial ferredoxins, shows enough homology with the latter group to suggest a common ancestor for the two types of ferredoxins. The amino acid sequence of a ferredoxin from a green photosynthetic bacterium will be very useful in tracing the evolutionary history of anaerobic bacteria. We have now determined the sequence of the ferredoxin I, one of the two ferredoxins from Chlorobium limicola which was purified from the extracts of Chloropseudomonas ethylicum. C. ethylicum is now considered to be a mixed culture of C. limicola and a nonphotosynthetic bacterium (Gray et al., 1972). W e have therefore also prepared ferredoxin from a pure culture of C. limicola kindly supplied to us by Dr. J. Olson. The amino acid composition and the amino acid sequence of amino-terminal region and carboxyl-terminus of a ferredoxin from C. limicola and of a ferredoxin from C. ethylicum whose sequence we are reporting are the same.
t From the Department of Biochemistry-Biophysics, University of Hawaii. Honolulu, Hawaii 96822 (M. T., M. H., and K. T. Y . ) . and the Botany Department, University of London King's College, London, England (M. C . W. E. and K . K. R.). Received January 31, 1974. This project was supported by Grants G M 16784 and G M 16228 from the National Institutes of Health, the National Science Foundation (GB 18739 and G B 43448), and the Science Research Council of Great Britain.
Experimental Section Materials. The bacteria was grown and the ferredoxin extracted as described by Rao et al. (1969). The ferredoxin was further purified by DEAE-cellulose column chromatography and gel filtration on Sephadex G-50. The purified protein had an A390/A280 ratio of 0.77. Reagent grade chemicals were used and their sources have been described in previous publications (Tanaka et al., 1971). Chymotrypsin was obtained from the Worthington Biochemical Corporation as three times crystallized preparation. Prior to the use, chymotrypsin was treated with L- 1-tosylamido-2-lysylethyl chloromethyl ketone (MaresGuia and Shaw, 1963). Thermolysin was purchased from Calbiochem. Methods. Non-Heme Iron, Labile Sulfur, and Amino Acid Composition. Iron and inorganic sulfide content was determined by standard methods (Harvey et a/., 1955; Fog0 and Popowsky, 1949; Lovenberg et a/., 1963) and was found to be 8 atoms each per molecule of ferredoxin assuming E390 = 30,000 mol-' cm-I. The amino acid composition of the protein and peptides was determined on acid hydrolysates in a BeckmanSpinco Model 12OC automatic amino acid analyzer as described by Spackman et al. (1958). The instrument was equipped with high sensitivity cuvets and a 4-5 mV full scale range card. NH2- and COOH-terminal Residues and Sequence Determinations. The NH2-terminal sequences of the Cml-ferredoxin were determined by the Beckman-Spinco Model 890 protein/ peptide sequencer utilizing the Protein Double Cleavage Pro-
'
The abbreviations used are: Cm-, S-@-carboxymethylcysteinyl-; Cys(Cm), S-P-carboxymethylcysteine; P T H , phenylthiohydantoin; BPA W, 1 -butanol-pyridine-acetic acid-water (60:40: 12:48, v / v ) ; BPW. I-butanol-pyridine-water (50:50:50, v/v) ; and TLCK, I.-] tosyl- amido-2-lysylethyl chloromethyl ketone. BIOCHEMISTRY,
VOL.
13,
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14, 1974
2953
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t I C , ( . K t I : L h w e x I - X 2 column chromatography of Chlorobium l i m i i,ula Cni-ferredoxin (about 9 mg). See Procedure for experimental details. Fr,icrions under each peak which were pooled a r e shown b? a .rolid bar
gram. The NHl-terminal sequences of all the other peptides were achieved by the usual manual Edman degradation method (Edman, and Sjoquist, 1956). The amino acid phenylthiohydantoins were identified by gas chromatography in a Beckman GC-45 gas chromatograph as described by Pisano and Rronzert ( I 969), or by thin-layer chromatography as described by Edinan and Begg ( 1 967), or by 6 N HCI hydrolysis of the amino acid phenylthiohydantoin to the free amino acids (Van Horten and Carpenter, 1969). The COOH-terminal amino acids \+ere determined by the use of carboxypeptidase A ( A m bler, 1967). Hydrazinolysis was performed on the protein and peptides as described by Bradbury ( 1 958). Procedures. Preparation and Chromatography of Cm-ferredoxin. The C. limicola ferredoxin was converted to its apoprotein by treating the native protein with trichloroacetic acid and then to the Cm derivative by reaction with iodoacetic acid as described in previous reports (Tanaka et al.. 1971). In a typical experiment, the Cin-ferredoxin preparation (about 9 mg) was applied to a Dowex I-X2 column ( 1 X 20 cm). Linear gradient elution was performed bl, addition of 200 ml of 8 M urea-2 VI acetic acid in the mixing chamber and 200 ml of 8 M urea-6 M acetic acid in the reservoir. The flou rate was 51 ml/hr and each fraction volume was 5.1 mi. The fractions were detected b> measuring absorbance a t 280 nm. C'hj~nrorrj~psin Digestion, Chromatographj oj. the Digest. c m l Further Purification of'the Peptides. About 3.5 pmol of Cm-ferredoxin (ferredoxin I ) was incubated with TLCK-chymotrypsin (enLynie to substrate was 1:30) at pH 8.0 in a total volume of 1.7 ml. Additional TLCK-chymotrypsin was added at 4 hr and the digestion was performed a t 28" for 16 hr. Chymotryptic digest of Cm-ferredoxin (1.75 pmol) was applied to a Sephadex G-75 column (1.5 X I 15 cm). The elution buffer was 0.1 M ammonia and the flow rate was 43 ml/hr. The fractions of 2.0 ml were collected and were detected bq the absorbance of the samples a t 233 nm. Peptides were further purified by paper chromatography in the solvent systems, I-butanolpyridine-acetic acid-water (60:40:12:48. v / v ) or I-butanolpqridine water (50:50:50,v/v). Thertno/j~fi~7 Pigestion
