title: Differential exposure of components of cytochrome b-c1 region in beef heart mitochondria and electron transport particles.
abstract: The reduction of cyctochromes c + c1 by durohydroquinone and ferrocyanide in electron transport particles (ETP) and intact cytochrome c-depleted beef heart mitochondria has been studied. At least 94% of the ETP are in an inverted orientation. Durohydroquinone reduces 80% of c + c1 in ETP but less than 20% in mitochondria; sonication of mitochondria allows reduction of cytochromes c + c1 (80%). Addition of ferrocyanide (effective redox potential +245 mV) to electron transport particles results in 30% reduction of cytochromes c + c1. Addition of ferrocyanide to intact cytochrome c-depleted mitochondria does not reduce cytochrome c1; treatment with N,N,N',N'-tetramethylphenylenediamine, Triton X-100, or sonic oscillation results in 30% reduction of cytochromes c + c1. The Km value of ferrocyanide oxidase for K-ferrocyanide is pH-dependent in ETP only, increasing with increasing pH. The extent of reduction of cytochrome c1 is also pH-dependent in ETP only, the extent of reduction increasing with decreasing pH. On the basis of these data cytochrome c1 is exposed to the matrix face and cytochrome c is exposed to the cytoplasmic face. No redox center other than cytochrome c in the segment between the antimycin site and cytochrome c is exposed on the C-side.
mesh_terms: D000818:Animals; D002417:Cattle; D003574:Cytochrome c Group / Q000378:metabolism; D003575:Cytochromes c1 / Q000378:metabolism; D004579:Electron Transport; D014450:Electron Transport Complex III; D005295:Ferrocyanides; D006873:Hydroquinones / Q000494:pharmacology; D007700:Kinetics; D008929:Mitochondria, Heart / Q000201:enzymology*; D009097:Multienzyme Complexes / Q000378:metabolism*; D009247:NADH, NADPH Oxidoreductases / Q000378:metabolism*; D010084:Oxidation-Reduction; D011808:Quinone Reductases / Q000378:metabolism*; D013367:Submitochondrial Particles / Q000201:enzymology
chemical_list: D003574:Cytochrome c Group; D005295:Ferrocyanides; D006873:Hydroquinones; D009097:Multienzyme Complexes; D003575:Cytochromes c1; D009247:NADH, NADPH Oxidoreductases; D011808:Quinone Reductases; D014450:Electron Transport Complex III; C016421:duroquinol