title: The action of tributyltin chloride on energy-dependent transhydrogenation of NADP+ by NADH in membranes of Escherichia coli.
abstract: Respiration- and ATP-dependent transhydrogenation of NADP+ by NADH in everted membrane vesicles from Escherichia coli is inhibited by nigericin but is relatively insensitive to valinomycin. The sensitivity to nigericin is enhanced 30-fold in the presence of valinomycin. It is concluded that both the transmembrane pH difference and the membrane potential constitute the driving force for energy-dependent transhydrogenation. Respiration- and ATP-dependent transhydrogenation are inhibited by tributyltin chloride. Although effects on the energization system have not been excluded, the inhibitor appears to react with a sulfhydryl group on the transhydrogenase enzyme. This inhibition is not dependent on the presence of a permeant anion and can be reversed by mono- and particularly di-thiol compounds. The transhydrogenase is also inhibited by 5,5'-dithiobis(2-nitrobenzoic acid), N-ethylmaleimide, p-chloromercuriphenyl sulfonic acid, and Zn2+, but these reagents are less effective than tributyltin chloride. Energy-independent transhydrogenation is inhibited at high concentrations (20 mM) of cysteine. The reason for this is unknown.
mesh_terms: D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism*; D004926:Escherichia coli / Q000187:drug effects / Q000378:metabolism*; D009243:NAD / Q000378:metabolism*; D009247:NADH, NADPH Oxidoreductases / Q000378:metabolism*; D009249:NADP / Q000378:metabolism*; D009250:NADP Transhydrogenases / Q000378:metabolism*; D009550:Nigericin / Q000494:pharmacology; D013439:Sulfhydryl Reagents / Q000494:pharmacology; D014634:Valinomycin / Q000494:pharmacology
chemical_list: D013439:Sulfhydryl Reagents; D009243:NAD; D014634:Valinomycin; D009249:NADP; D009247:NADH, NADPH Oxidoreductases; D009250:NADP Transhydrogenases; D009550:Nigericin