A study is presented of the effect of acidic uncouplers and oligomycin on energy-linked and passive proton translocation, oxidative phosphorylation, and energy-linked nicotinamide-adenine-nucleotide transhydrogenase in EDTA submitochondrial particles from beef-heart. A flow potentiometric technique has been applied to resolve the kinetics of the initial rapid phase of the redox proton pump. Rapid kinetics analysis shows that carbonyl-cyanide-p-trifluoromethoxyphenyl-hydrazone (FCCP) does not exert any direct effect on redox-linked active proton transport. The uncoupling action of FCCP on oxidative phosphorylation and energy-linked transhydrogenase is shown to be quantitatively accounted for by its promoting effect of passive proton-diffusion across the mitochondrial membrane. Oligomycin depresses passive proton diffusion in EDTA sonic particles and this effect accounts for the coupling action exerted by the antibiotic on oxidative phosphorylation and energy-linked transhydrogenase. In fact, rapid kinetic analysis demonstrates that oligomycin does not directly affect the redox-linked proton pump. The present results show that there does not exist any labile intermediate in the redox-linked proton pump which is sensitive to acidic uncouplers.

Animals↗

PubMed1975

Studies on the characteristics of a proton pump in phospholipid vesicles inlayed with purified complex III from beef heart mitochondria.

Explore the source record for details and available documents.

Animals↗

PubMed1975

Mechanism of respiration-driven proton translocation in the inner mitochondrial membrane. Analysis of proton translocation associated with oxidation of endogenous ubiquinol.

A study is presented of the kinetics and stoichiometry of fast proton translocation associated to aerobic oxidation of components of the mitochondrial respiratory chain. 1. Aerobic oxidation of ubiquinol and b cytochromes is accompanied in EDTA particles, obtained by sonication of beef-heart mitochondria, by synchronous proton uptake. 2. The rapid proton uptake associated to oxidation and b cytochromes is greatly stimulated by valinomycin plus K+, but is unaffected by carbonyl cyanide p-trifluoromethoxyphenylhydrazone. 3. 4 gion H+ are taken up per mol ubiquinol oxidized by oxygen. This H+/2e- ratio, measured in the rapid anaerobic-aerobic transition of the particles is unaffected by carbonyl cyanide p-trifluoromethoxyphenylhydrazone. 4. Intact mitochondria aerobic oxidation of oxygen-terminal electron carriers is accompanied by antimycin-insensitive synchronous proton release, oxidation of ubiquinol and reduction of b cytochromes. The amount of protons released is in excess with respect to the amount of ubiquinol oxidized. 5. It is concluded that electron flow along complex III, from ubiquinol to cytochrome c, is directly coupled to vectorial proton translocation. The present data suggest that there exist(s) between ubiquinol and cytochrome c one (or two) respiratory carrier(s), whose oxido-reduction is directly linked to effective transmembrane proton translocation.

Animals↗