title: Interactions of cytochrome c with mitochondrial membranes. Binding to succinate-cytochrome c reductase.
abstract: Methyl-4-azidobenzoimidate was reacted with horse heart cytochrome c to give a photoaffinity-labeled derivative of this heme protein. The modified cytochrome c bound to cytochrome c-depleted mitochondria with the same Kd as native cytochrome c and restored oxygen uptake to the same extent. Irradiation of cytochrome c-depleted mitochondrial membranes with 3- to 4-fold excess of photoaffinity-labeled cytochrome c over cytochrome c oxidase resulted in covalent binding of the derivative to the membranes. Fractionation of the irradiated mitochondria in the presence of detergents and salts followed by chromatography on an agarose Bio-Gel-A-5m showed that the labeled cytochrome c was bound covalently to succinate-cytochrome c reductase. The covalently bound cytochrome c was active in mediating electron transfer between its reductase and oxidase. Sodium dodecyl sulfate polyacrylamide gel electrophoresis of the succinate-cytochrome c reductase containing photoaffinity-labeled 125I-cytochrome c showed that the reductase contained a protein binding site for cytochrome c. It is suggested that cytochrome c1 is the most likely site for the cytochrome c binding in mitochondria in situ.
mesh_terms: D000345:Affinity Labels; D000818:Animals; D001386:Azides; D010856:Columbidae; D003574:Cytochrome c Group / Q000378:metabolism*; D004227:Dithionite; D007096:Imidoesters; D007425:Intracellular Membranes / Q000201:enzymology; D007700:Kinetics; D008930:Mitochondria, Liver / Q000201:enzymology*; D008931:Mitochondria, Muscle / Q000378:metabolism*; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000378:metabolism*; D011485:Protein Binding; D051381:Rats; D013053:Spectrophotometry; D013384:Succinate Cytochrome c Oxidoreductase / Q000378:metabolism*; D013386:Succinates
chemical_list: D000345:Affinity Labels; D001386:Azides; D003574:Cytochrome c Group; D007096:Imidoesters; D013386:Succinates; D004227:Dithionite; C026810:methyl 4-azidobenzimidate; D010088:Oxidoreductases; D013384:Succinate Cytochrome c Oxidoreductase