The proton pump of cytochrome c oxidase and its stoichiometry.
The operation of cytochrome c oxidase with ascorbate/N,N,N',N'-tetramethyl-p-phenylenediamine as substrate in antimycin-A-inhibited rat liver mitochondria is coupled to proton ejection. Measurements of the initial rate of valinomycin-dependent K+ uptake have shown that nearly 4 K+ are taken up as 2 electrons are transferred from cytochrome c to oxygen. This proves directly that a charge separation of nearly 4 occurs across the inner mitochondrial membrane each time 2 electrons are transferred to oxygen. Measurements of the initial rate of proton movement after addition of the reductant show that about 1.6 protons are released by the mitochondria as 2 electrons are transferred from cytochrome c to oxygen. The data support the suggestion of a proton pump coupled to the operation of cytochrome c oxidase [Wikström, M. F. K. (1977) Nature (Lond.) 266, 271--273].
D000818:Animals; D000968:Antimycin A / Q000494:pharmacology; D004579:Electron Transport; D003576:Electron Transport Complex IV / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007425:Intracellular Membranes / Q000378:metabolism; D007700:Kinetics; D008930:Mitochondria, Liver / Q000187:drug effects / Q000201:enzymology*; D010101:Oxygen Consumption; D011188:Potassium; D051381:Rats; D013772:Tetramethylphenylenediamine
D000968:Antimycin A; D003576:Electron Transport Complex IV; D013772:Tetramethylphenylenediamine; D011188:Potassium