title: Two-electron reduction of cytochrome c oxidase triggers a conformational transition.
abstract: The slow increase of a cyanide-induced optical change at 437 nm following rapid cyanide inhibition of cytochrome oxidase has been followed as a function of the number of electrons donated from ferrocytochrome c to cytochrome a and CuA. The initial rate of optical change is a parabolic function of this number. The results have been analyzed in terms of a model where addition of electrons causes a conformational transition allowing rapid cyanide binding. The binding is followed by a slow intramolecular responsible for the optical change. The analysis demonstrates that only molecules with both cytochrome a and CuA reduced can undergo the conformational change, which is suggested to be involved in the proton-pump mechanism of the oxidase.
mesh_terms: D000818:Animals; D002417:Cattle; D003486:Cyanides / Q000494:pharmacology; D017936:Cytochrome a Group; D003580:Cytochromes; D003576:Electron Transport Complex IV / Q000037:antagonists & inhibitors; D007700:Kinetics; D010084:Oxidation-Reduction; D011487:Protein Conformation; D011522:Protons
chemical_list: D003486:Cyanides; D017936:Cytochrome a Group; D003580:Cytochromes; D011522:Protons; D003576:Electron Transport Complex IV