InterPro domain: IPR027387

Cytochrome b/b6 [ 1 , 2 ] is an integral membrane protein of approximately 400 amino acid residues that probably has 8 transmembrane segments. In plants and cyanobacteria, cytochrome b6 consists of two subunits encoded by the petB and petD genes. The sequence of petB is colinear with the N-terminal part of mitochondrial cytochrome b, while petD corresponds to the C-terminal part. Cytochrome b/b6 non-covalently binds two haem groups, known as b562 and b566. Four conserved histidine residues are postulated to be the ligands of the iron atoms of these two haem groups [ 3 , 3 ].

1. Evolutionary conservation of protein regions in the protonmotive cytochrome b and their possible roles in redox catalysis. J. Mol. Evol. 29, 157-69
2. Mitochondrial cytochrome b: evolution and structure of the protein. Biochim. Biophys. Acta 1143, 243-71