Molecular Complexes between Cytochrome b2 [Yeast L(+)Lactate: Cytochrome c Oxidoreductase] and Cytochrome c in the Crystalline State and in Solution

In the crystalline state and in solution, cytochrome b2 (yeast l‐lactate: cytochrome c oxidoreductase) is shown to form a very stable complex with cytochrome c (from horse heart or yeast). This complex is characterized by a cytochrome c/cytochrome b2 heme ratio of about 0.25 which corresponds to the binding of one cytochrome c molecule to one tetraheme enzyme unit. Its formation is pH sensitive and prevented by salts but not by antimycin A. The prosthetic flavin group of cytochrome b2 is not required for the binding of cytochrome c.