Bifurcated ubihydroquinone oxidation in the cytochrome bc1 complex by proton-gated charge transfer.
The unique bifurcation of electron flow at the ubihydroquinone-oxidation center of the cytochrome bc1 complex is the energy-conserving reaction of the protonmotive Q- cycle and is prerequisite to vectorial proton translocation. The widely accepted Q-cycle reaction scheme describes the overall electron and proton pathways, but does not address the detailed chemistry of this central step. Based on a model of the ubihydroquinone-oxidation pocket containing two ubiquinone molecules in a stacked configuration, a detailed model for the reactions during steady-state catalysis is proposed. In this proton-gated charge-transfer mechanism the reaction is controlled by the deprotonation of the substrate ubihydroquinone.
Brandt
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Universitätsklinikum Frankfurt, Zentrum der Bioligischen Chemie, Frankfurt am Main, Germany. brandt@zbc.klinik.uni-frankfurt.de
D004579:Electron Transport; D014450:Electron Transport Complex III / Q000737:chemistry* / Q000378:metabolism; D008956:Models, Chemical; D015394:Molecular Structure; D010084:Oxidation-Reduction; D011522:Protons
D011522:Protons; D014450:Electron Transport Complex III