ATP synthase complex from bovine heart mitochondria. Passive H+ conduction through F0 does not require oligomycin sensitivity-conferring protein.
Oligomycin sensitivity-conferring protein (OSCP) is a water-soluble subunit of bovine heart mitochondrial H(+)-ATPase (F1-F0). In order to investigate the requirement of OSCP for passive proton conductance through mitochondrial F0, OSCP-depleted membrane preparations were obtained by extracting purified F1-F0 complexes with 4.0 M urea. The residual complexes, referred to as UF0, were found to be deficient with respect to OSCP, as well as alpha, beta, and gamma subunits of F1-ATPase, but had a full complement of coupling factor 6 as judged by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blotting techniques. These UF0 complexes had no intrinsic ATPase activity and were able to bind nearly the same amount of F1-ATPase in the presence of either OSCP or NH4+ ions alone, or a combination of the two. However, the preparations exhibited an absolute dependency on OSCP for conferral of oligomycin sensitivity to membrane-bound ATPase. The passive proton conductance in UF0 proteoliposomes was measured by time-resolved quenching of 9-amino-6-chloro-2-methoxyacridine or 9-aminoacridine fluorescence following a valinomycin-induced K(+)-diffusion potential. The data clearly establish that OSCP is not a necessary component of the F0 proton channel nor is its presence required for conductance blockage by the inhibitors oligomycin or dicyclohexylcarbodiimide. Furthermore, OSCP does not prevent or block passive H+ leakage. Comparisons of OSCP with the F1-F0 subunits from Escherichia coli and chloroplast lead us to suggest that mitochondrial OSCP is, both structurally and functionally, a hybrid between the beta and delta subunits of the prokaryotic systems.
Pringle
M J
MJ
Boston Biomedical Research Institute, Department of Cell Physiology, Massachusetts 02114.
Kenneally
M K
MK
Joshi
S
S
D000251:Adenosine Triphosphatases / Q000302:isolation & purification / Q000378:metabolism*; D000818:Animals; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone / Q000494:pharmacology; D002352:Carrier Proteins / Q000378:metabolism; D002417:Cattle; D007106:Immune Sera; D007700:Kinetics; D008081:Liposomes; D046911:Macromolecular Substances; D008565:Membrane Proteins / Q000302:isolation & purification / Q000378:metabolism*; D008929:Mitochondria, Heart / Q000201:enzymology*; D025261:Mitochondrial Proton-Translocating ATPases; D008954:Models, Biological; D008970:Molecular Weight; D009840:Oligomycins / Q000378:metabolism*; D011510:Proteolipids / Q000378:metabolism; D006180:Proton-Translocating ATPases / Q000378:metabolism*; D011522:Protons; D014634:Valinomycin / Q000494:pharmacology
D002352:Carrier Proteins; D007106:Immune Sera; D008081:Liposomes; D046911:Macromolecular Substances; D008565:Membrane Proteins; D009840:Oligomycins; D011510:Proteolipids; D011522:Protons; C020485:proteoliposomes; D014634:Valinomycin; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone; D000251:Adenosine Triphosphatases; D025261:Mitochondrial Proton-Translocating ATPases; D006180:Proton-Translocating ATPases; C020439:oligomycin sensitivity-conferring protein