AMINO-ACID SEQUENCE OF MAJOR COMPONENT OF APHANOTHECE-SACRUM FERREDOXIN

Chymotryptic and tryptic peptides of carboxymethyl-ferredoxin and chymotryptic peptides of oxidized ferredoxin were prepared and their sequences analyzed. The complete amino acid sequence consisted of 96 amino acid residues with 5 cysteine residues. The cysteine residue at the 18th position usually found in other chloroplast-type ferredoxins was replaced by a valine residue and the cysteine residue at the 85th position was common with that in Scenedesmus ferredoxin. The sequence was Ala-Ser-Tyr-Lys-Val-Thr-Leu-Lys-Thr-Pro-Asp-Gly-Asp-Asn-Val-Ile-Thr-Val-Pro-Asp-Asp-Glu-Tyr-Ile-Leu-Asp-Val-Ala-Glu-Glu-Glu-Gly-Leu-Asp-Leu-Pro-Tyr-Ser-Cys-Arg-Ala-Gly-Ala-Cys-Ser-Thr-Cys-Ala-Gly-Lys-Leu-Val-Ser-Gly-Pro-Ala-Pro-Asp-Glu-Asp-Gln-Ser-Phe-Leu-Asp-Asp-Asp-Gln-Ile-Gln-Ala-Gly-Tyr-Ile-Leu-Thr-Cys-Val-Ala-Tyr-Pro-Thr-Gly-Asp-Cys-Val-Ile-Glu-Thr-His-Lys-Glu-Glu-Ala-Leu-Tyr. Calculation of the numbers of amino acid differences among chloroplast-type ferredoxins indicated that the Aphanothece ferredoxin was far divergent, not only from higher plant ferredoxins, but also from Spirulina ferredoxins and blue-green algal ferredoxins. Some comments on the evolution of ferredoxins are presented.