Electrogenic proton ejection coupled to electron transport through the energy-conserving site 2 and K+/H+ exchange in yeast mitochondria.
The proton ejection coupled to electron flow from succinate and/or endogenous substrate(s) to cytochrome c using the impermeable electron acceptor ferricyanide is studied in tightly coupled mitochondria isolated from two strains of the yeast Saccharomyces cerevisiae. (1) The observed H+ ejection/2e- ratio approaches an average value of 3 when K+ (in the presence of valinomycin) is used as charge-compensating cation. (2) In the presence of the proton-conducting agent carbonyl cyanide m-chlorophenylhydrazone, an H+ ejection/2e- ratio of 2 is observed. (3) The low stoichiometry of 3H+ ejected (instead of 4) per 2e- and the high rate of H+ back-decay (0.1615 ln delta (ngatom)H+/s and a half-time of 4.6 s for 10 mg protein) into the mitochondrial matrix are related to the presence of an electroneutral K+/H+ antiporter which is demonstrated by passive swelling experiments in isotonic potassium acetate medium.
D000968:Antimycin A / Q000494:pharmacology; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone / Q000494:pharmacology; D003574:Cytochrome c Group / Q000378:metabolism; D004579:Electron Transport; D006859:Hydrogen / Q000378:metabolism*; D008928:Mitochondria / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D013386:Succinates / Q000378:metabolism; D019802:Succinic Acid; D014634:Valinomycin / Q000494:pharmacology
D003574:Cytochrome c Group; D013386:Succinates; D014634:Valinomycin; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone; D000968:Antimycin A; D006859:Hydrogen; D019802:Succinic Acid; D011188:Potassium