Protonmotive functions of cytochrome c oxidase in reconstituted vesicles. Influence of turnover rate on 'proton translocation'.
1. Oxidation of ferrocytochrome c by cytochrome c oxidase incorporated into proteoliposomes induces a transient acidification of the external medium. This change is dependent on the presence of valinomycin and can be abolished by carbonyl cyanide p-trifluoromethoxyphenylhydrazone or by nigericin. The H+/e- ratio for the initial acidification varies with the internal buffering capacity of the vesicles, and under suitable conditions approaches + 1, the pulse slowly decaying to give a net alkalinity change with H+/e- value approaching -1. 2. Inhibition of cytochrome c oxidase turnover by ferricytochrome c or by azide addition results in ferrocytochrome c-dependent H+ pulses with decreasing H+/e- ratios. The rate of the initial H+ production remains higher than the rate of equilibration of the pH gradient, indicating an intrinsic dependence of the H+/e- ratio on enzyme turnover. The final net alkalinity changes are relatively unaffected by turnover inhibition.
D000332:Aerobiosis; D001386:Azides / Q000494:pharmacology; D003574:Cytochrome c Group / Q000378:metabolism; D004563:Electrochemistry; D003576:Electron Transport Complex IV / Q000037:antagonists & inhibitors / Q000378:metabolism*; D004910:Erythrocyte Membrane / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007202:Indicators and Reagents / Q000494:pharmacology; D007700:Kinetics; D008081:Liposomes / Q000378:metabolism; D010084:Oxidation-Reduction; D011510:Proteolipids / Q000378:metabolism; D011522:Protons; D019810:Sodium Azide
D001386:Azides; D003574:Cytochrome c Group; D007202:Indicators and Reagents; D008081:Liposomes; D011510:Proteolipids; D011522:Protons; C020485:proteoliposomes; D019810:Sodium Azide; D003576:Electron Transport Complex IV