Structural gene of cytochrome b-562 from the cytochrome b-c₁ complex of Rhodobacter sphaeroides

The structural gene coding for cytochrome b-562 isolated from the cytochrome b-c₁ complex of Rhodobacter (Rhodopseudomonas) sphaeroides has been cloned. Its nucleotide sequence has been determined and the amino acid sequence was deduced therefrom. It consists of 157 amino acids M_r 17,237) and contains four hydro-phobic segments. The first 30 residues in the predicted amino acid sequence are the same as those determined for the NH₂,-terminal portion of purified cytochrome b-562. The amino acid composition is in accord with that determined for the pure protein. From the hydropathy profile and molar ratio of protoheme to cytochrome b-562, it is suggested that the structural and functional unit of the cytochrome is a two-heme cross-linked homodimer.