The amino acid sequence of Chromatium ferredoxin.

The amino acid sequence of Chromatium ferredoxin was determined by studies of thermolysin peptides of S-carboxymethylcysteinylferredoxin and chymotryptic peptides of oxidized ferredoxin. The 81 amino acid residues in the molecule have the following sequence: Ala-Leu-Met-IleThr-Asp-Gln-Cys-Ile-Asn-Cys-Asn-Val-Cys-Gln-ProGlu-Cys-Pro-Asn-Gly-Ala-Ile-Ser-Gln-Gly-Asp-Glu-ThrTyr-Val-Ile-Glu-Pro-Ser-Leu-Cys-Thr-Glu-Cys-Val-GlyHis-Tyr-Glu-Thr-Ser-Gln-Cys-Val-Asp-Cys-Val-GluVal-Cys-Pro-Ile-Lys-Asp-Pro-Ser-His-Glu-Glu-ThrGlu-Asp-Glu-Leu-Arg-Ala-Lys-Tyr-Glu-Arg-Ile-ThrGly-Glu-Gly. The molecular weight, excluding iron and inorganic sulfide, was calculated to be 8943. The 9 cysteinyl residues are located in a somewhat different manner from those of the ferredoxins of nonphotosynthetic bacteria. However, this sequence is apparently homologous to those of nonphotosynthetic bacterial f erredoxins. Some structural features of bacterial ferredoxins are compared.