title: Spectroscopic analysis of the interaction between cytochrome c and cytochrome c oxidase.
abstract: Complex formation between cytochrome c oxidase and cytochrome c perturbs the optical absorption spectrum of heme c and heme a in the region of the alpha-, beta, and gamma-bands. The perturbations have been used to titrate cytochrome c oxidase with cytochrome c. A stoichiometry of one molecule of cytochrome c bound per molecule of cytochrome c oxidase is obtained (1 heme c per heme aa3). In contrast, a stoichiometry of 2:1 was found earlier using a gel-filtration method (Rieder, R., and Bosshard, H.R. (1978) J. Biol. Chem. 253, 6045-6053). From the result of the spectrophotometric titration and from the wavelength position of the perturbation signals it is concluded that cytochrome c oxidase contains only a single binding site for cytochrome c which is close enough to heme a to function as an electron transfer site. The second site detected earlier by the gel-filtration method must be remote from this electron transfer site. Scatchard plots of the titration data are curvilinear, possibly indicating interactions between cytochrome c-binding sites on adjacent monomers of dimeric cytochrome c oxidase. The relationship between cytochrome c binding and the reaction of cytochrome c oxidase with ferrocytochrome c is discussed.
mesh_terms: D000818:Animals; D002417:Cattle; D003574:Cytochrome c Group / Q000378:metabolism*; D003576:Electron Transport Complex IV / Q000378:metabolism*; D007700:Kinetics; D009206:Myocardium / Q000201:enzymology; D010084:Oxidation-Reduction; D010101:Oxygen Consumption; D011048:Polarography; D011485:Protein Binding; D013053:Spectrophotometry
chemical_list: D003574:Cytochrome c Group; D003576:Electron Transport Complex IV