title: Environment of the sulfhydryl groups in bovine heart mitochondrial H+-ATPase.
abstract: Electron transport particles and purified H+-ATPase (F1-F0) vesicles from beef heart mitochondria have been treated with two classes of thiol reagent, viz. membrane-impermeable organomercurials and a homologous series of N-polymethylene carboxymaleimides (Mal-(CH2)x-COOH or AMx). The effect of such treatment on ATP-driven reactions (ATP-Pi exchange and proton translocation) has been examined and compared to the effects on rates of ATP hydrolysis. The organomercurials inhibited ATP-Pi exchange and one of them (p-chloromercuribenzoate) inhibited ATPase activity. Of the maleimide series (AMx), AM10 and AM11 inhibited both ATP-Pi exchange and ATP-driven membrane potential, but not ATPase activity. The other members of the series were essentially inactive. N-Ethylmaleimide was intermediate in its efficacy. Passive H+ conductance through the membrane sector F0 was 50% blocked by AM10, slightly blocked by AM2 and N-ethylmaleimide, and unaffected by the other members of the AMx series. The data imply that one -SH near the membrane surface and one -SH about 12 A from the surface are functional in proton translocation through the H+-ATPase.
mesh_terms: D002731:4-Chloromercuribenzenesulfonate / Q000494:pharmacology; D000818:Animals; D002417:Cattle; D004579:Electron Transport / Q000187:drug effects; D008301:Maleimides; D008929:Mitochondria, Heart / Q000201:enzymology* / Q000648:ultrastructure; D009941:Organomercury Compounds / Q000494:pharmacology; D010618:Phenanthrolines / Q000494:pharmacology; D006180:Proton-Translocating ATPases / Q000037:antagonists & inhibitors*; D013329:Structure-Activity Relationship; D013439:Sulfhydryl Reagents / Q000494:pharmacology*
chemical_list: D008301:Maleimides; D009941:Organomercury Compounds; D010618:Phenanthrolines; D013439:Sulfhydryl Reagents; D002731:4-Chloromercuribenzenesulfonate; D006180:Proton-Translocating ATPases; C025205:1,10-phenanthroline