Thiols in oxidative phosphorylation: inhibition and energy-potentiated uncoupling by monothiol and dithiol modifiers.
Three apparently different modifications of submitochondrial particles (SMP) or ATP synthase preparations (complex V) inhibit oxidative phosphorylation and ATP-32Pi exchange activities, all of which are reversible by addition of mono- or dithiols. (a) Triphenyltin chloride inhibits ATP synthesis and hydrolysis without uncoupling. The inhibition by triphenyltin chloride is reversible by addition of beta-mercaptoethanol, dithiothreitol, or dihydrolipoamide. (b) Factor B is a water-soluble protein of Mr (11-12) X 10(3), contains a vicinal dithiol, and is required for energy transfer to and from F1-ATPase when tested with SMP-rendered factor B deficient by extraction with ammonia-ethylenediaminetetraacetic acid (EDTA) (AE-SMP). Treatment of factor B with mono- and dithiol modifiers, such as p-(chloromercuri)benzenesulfonate (PCMPS), Cd2+, or diazenedicarboxylic acid bis(dimethylamide) (diamide), inhibits factor B. This inhibition is reversed by addition to modified factor B of appropriate mono- and dithiol compounds. Preparations of AE-SMP are partially F1 deficient and partially uncoupled. The uncoupling can be repaired completely by addition of factor B or low levels of oligomycin, or to a large extent by addition of F1-ATPase + oligomycin sensitivity conferring protein. (c) SMP, AE-SMP, and complex V can be completely uncoupled by treatment at 30 degrees C with phenylarsine oxide, Cd2+, diamide, PCMPS, monobromobimane, and mono- and bifunctional maleimides. The uncoupling by these reagents is potentiated by membrane energization. Uncoupling by diamide is greater than or equal to 80% reversed by dihydrolipoamide or beta-mercaptoethanol, the former being much more potent. Dithiothreitol and dithioerythritol are poorly effective.(ABSTRACT TRUNCATED AT 250 WORDS)
D000818:Animals; D002417:Cattle; D003958:Diamide / Q000494:pharmacology; D007700:Kinetics; D008564:Membrane Potentials / Q000187:drug effects; D008929:Mitochondria, Heart / Q000187:drug effects / Q000378:metabolism*; D010085:Oxidative Phosphorylation / Q000187:drug effects*; D010086:Oxidative Phosphorylation Coupling Factors; D010101:Oxygen Consumption / Q000187:drug effects; D013367:Submitochondrial Particles / Q000187:drug effects / Q000378:metabolism*; D013438:Sulfhydryl Compounds / Q000032:analysis; D013439:Sulfhydryl Reagents / Q000494:pharmacology*
D010086:Oxidative Phosphorylation Coupling Factors; D013438:Sulfhydryl Compounds; D013439:Sulfhydryl Reagents; D003958:Diamide