Cytochrome b reduction by hexaammineruthenium in mitochondria and submitochondrial particles. Evidence for heme b-562 localization at the M-side of the mitochondrial membrane.

In the presence of ascorbate, hexaamineruthenium mediates rapid reduction of cytochrome b-562 in submitochondrial particles but not in mitochondria. The reaction is observed in the combined presence of antimycin (or funiculosin) and myxothiazol, which implies direct interaction of Ru(NH3)2+6 with b cytochrome(s). We assume that contrary to previous conclusions (Case and Leigh (1976) Biochem. J., 160, 769-783) redox centre of at least one of the oxidized cytochromes b, most probably of b-562, is exposed to the M-aqueous phase.