Anomalies in amino acid sequences of small cytochromes c and cytochromes c′ from two species of purple photosynthetic bacteria

Abstract

MOST species of the Rhodospirillaceae¹, the purple nonsulphur photosynthetic bacteria, produce large quantities of cytochrome c₂ (ref. 2), a protein which is similar in sequence to mitochondrial cytochrome c³. Many species also produce the high-spin haem protein cytochrome c′ (ref 2). Cytochromes c′ have been identified in Rhodopseudomonas gelatinosa and in Rhodospirillum tenue, but in these organisms the predominant low-spin cytochromes c do not have properties similar to those found for cytochromes c₂ (ref. 2). We have now determined the amino acid sequences of the cytochromes c′ and of the predominant low-spin cytochromes c from the two organisms (Fig. 1).