title: Inhibition of proton pumping in membrane reconstituted bovine heart cytochrome c oxidase by zinc binding at the inner matrix side.
abstract: A study is presented on the effect of zinc binding at the matrix side, on the proton pump of purified liposome reconstituted bovine heart cytochrome c oxidase (COV). Internally trapped Zn(2+) resulted in 50% decoupling of the proton pump at level flow. Analysis of the pH dependence of inhibition by internal Zn(2+) of proton release in the oxidative and reductive phases of the catalytic cycle of cytochrome c oxidase indicates that Zn(2+) suppresses two of the four proton pumping steps in the cycle, those taking place when the 2 OH(-) produced in the reduction of O(2) at the binuclear center are protonated to 2 H(2)O. This decoupling effect could be associated with Zn(2+) induced conformational alteration of an acid/base cluster linked to heme a(3).
authors.affiliation: Department of Medical Biochemistry, Biology and Physics, University of Bari, Italy.
authors.forename: Pietro Luca
authors.initials: PL
authors.lastname: Martino
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Capitanio
authors.forename: Nazzareno
authors.initials: N
authors.lastname: Capitanio
authors.forename: Sergio
authors.initials: S
authors.lastname: Papa
mesh_terms: D000818:Animals; D002417:Cattle; D003576:Electron Transport Complex IV / Q000378:metabolism*; D008081:Liposomes; D009206:Myocardium / Q000201:enzymology*; D010084:Oxidation-Reduction; D011485:Protein Binding; D011522:Protons; D015032:Zinc / Q000378:metabolism*
chemical_list: D008081:Liposomes; D011522:Protons; D003576:Electron Transport Complex IV; D015032:Zinc