Proton pumping mechanism and catalytic cycle of cytochrome c oxidase: Coulomb pump model with kinetic gating.
Using electrostatic calculations, we have examined the dependence of the protonation state of cytochrome c oxidase from bovine heart on its redox state. Based on these calculations, we propose a possible scheme of redox-linked proton pumping. The scheme involves His291 - one of the ligands of the Cu(B) redox center - which plays the role of the proton loading site (PLS) of the pump. The mechanism of pumping is based on ET reaction between two hemes of the enzyme, which is coupled to a transfer of two protons. Upon ET, the first proton (fast reaction) is transferred to the PLS (His291), while subsequent transfer of the second "chemical" proton to the binuclear center (slow reaction) is accompanied by the ejection of the first (pumped) proton. Within the proposed model, we discuss the catalytic cycle of the enzyme.
Popović
Dragan M
DM
Department of Chemistry, University of California, One Shields Avenue, Davis, CA 95616, USA.
Stuchebrukhov
Alexei A
AA
D000818:Animals; D001665:Binding Sites; D002384:Catalysis; D002417:Cattle; D003576:Electron Transport Complex IV / Q000737:chemistry* / Q000378:metabolism*; D006639:Histidine / Q000737:chemistry / Q000378:metabolism; D007700:Kinetics; D008956:Models, Chemical; D008958:Models, Molecular; D009206:Myocardium / Q000201:enzymology; D010084:Oxidation-Reduction; D017494:Proton Pumps / Q000737:chemistry* / Q000378:metabolism*; D055672:Static Electricity
D017494:Proton Pumps; D006639:Histidine; D003576:Electron Transport Complex IV