Activity of proteoliposomes containing cytochrome oxidase in the submitochondrial orientation.
Cytochrome-c oxidase proteoliposomes containing internally trapped cytochrome c can turn over on internal or external cytochrome c. At low TMPD levels the internal activity is significantly lower than the external activity as the functional internal cytochrome c is not fully reduced in the steady state. Increasing TMPD concentration increases the internal rate to equal that of the external enzyme. Internal activity results in the accumulation of TMPD+. Valinomycin increases this accumulation and subsequently FCCP decreases it. In the presence of excess external cytochrome c, the effects of these ionophores are reversed. The internally-facing enzyme is thus capable of generating a delta mu H+ in proteoliposomes as well as in submitochondrial particles.
Cooper
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CE
Department of Biological Sciences, Brock University, St. Catharines, Ontario, Canada.
Nicholls
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D000818:Animals; D002417:Cattle; D003574:Cytochrome c Group / Q000378:metabolism*; D003576:Electron Transport Complex IV / Q000378:metabolism*; D066298:In Vitro Techniques; D007476:Ionophores / Q000494:pharmacology; D007700:Kinetics; D008564:Membrane Potentials; D010084:Oxidation-Reduction; D011510:Proteolipids; D013367:Submitochondrial Particles / Q000378:metabolism* / Q000648:ultrastructure; D013772:Tetramethylphenylenediamine / Q000378:metabolism
D003574:Cytochrome c Group; D007476:Ionophores; D011510:Proteolipids; C020485:proteoliposomes; D003576:Electron Transport Complex IV; D013772:Tetramethylphenylenediamine