title: The site of inhibition by 5,5'-dithiobis(2-nitrobenzoate) in ubiquinol: cytochrome c oxidoreductase.
abstract: In 5,5'-dithiobis(2-nitrobenzoate) (DTNB)-treated succinate: cytochrome c reductase, the electron transfer from duroquinol to cytochrome c is inhibited due to the fact that the Rieske Fe-S cluster and, consequently, cytochrome, c, are no longer reducible by substrate. The finding that, after this treatment, cytochrome b is still reducible by substrate in the absence of antimycin, but not in its presence, is consistent with a Q-cycle mechanism for the electron transfer through QH2:cytochrome c oxidoreductase. The inhibitory effect of DTNB and its effect on the EPR spectrum of the [2Fe-2S] cluster suggest that it prevents either the binding of ubiquinone in the vicinity of this cluster or the interaction between the Fe-S protein and a ubiquinone-binding protein.
mesh_terms: D003573:Cytochrome b Group / Q000378:metabolism; D003574:Cytochrome c Group / Q000378:metabolism; D004228:Dithionitrobenzoic Acid / Q000494:pharmacology*; D004578:Electron Spin Resonance Spectroscopy; D004579:Electron Transport; D014450:Electron Transport Complex III; D007506:Iron-Sulfur Proteins / Q000378:metabolism; D007700:Kinetics; D009097:Multienzyme Complexes / Q000037:antagonists & inhibitors*; D009247:NADH, NADPH Oxidoreductases / Q000037:antagonists & inhibitors*; D009579:Nitrobenzoates / Q000494:pharmacology*; D011808:Quinone Reductases / Q000037:antagonists & inhibitors*; D013379:Substrate Specificity
chemical_list: D003573:Cytochrome b Group; D003574:Cytochrome c Group; D007506:Iron-Sulfur Proteins; D009097:Multienzyme Complexes; D009579:Nitrobenzoates; D004228:Dithionitrobenzoic Acid; D009247:NADH, NADPH Oxidoreductases; D011808:Quinone Reductases; D014450:Electron Transport Complex III