title: The pathway of electron transfer in the dimeric QH2: cytochrome c oxidoreductase.
abstract: The experimental data currently available suggest that QH2:cytochrome c oxidoreductase functions according to a Q-cycle type of mechanism. The molecular weight of the enzyme in a natural or artificial phospholipid bilayer or in solution corresponds to that of a dimer. The pre-steady state kinetics of reduction of the prosthetic groups indicate that the enzyme is functionally dimeric. A double Q cycle is proposed, describing the pathway of electron transfer in the dimeric QH2:cytochrome c oxidoreductase. According to this scheme, the two monomeric halves of the enzyme act in a cooperative fashion to complete the catalytic cycle. It is proposed that high-potential cytochrome b-562 and low-potential cytochrome b-562 act cooperatively, viz. as a functional pair, in the antimycin-sensitive reduction of ubiquinone to ubiquinol.
mesh_terms: D000818:Animals; D002417:Cattle; D003573:Cytochrome b Group / Q000378:metabolism; D004578:Electron Spin Resonance Spectroscopy; D004579:Electron Transport; D003576:Electron Transport Complex IV / Q000378:metabolism*; D029968:Escherichia coli Proteins; D006873:Hydroquinones / Q000378:metabolism*; D007425:Intracellular Membranes / Q000378:metabolism; D007700:Kinetics; D008958:Models, Molecular; D008970:Molecular Weight; D009097:Multienzyme Complexes / Q000378:metabolism*; D011199:Potentiometry; D013816:Thermodynamics; D014451:Ubiquinone / Q000378:metabolism*
chemical_list: D003573:Cytochrome b Group; D029968:Escherichia coli Proteins; D006873:Hydroquinones; D009097:Multienzyme Complexes; D014451:Ubiquinone; C017850:cytochrome b562, E coli; D003576:Electron Transport Complex IV