title: Conformational change of cytochrome a3 induced by oxidized cytochrome c.
abstract: Cyanide binding with the oxidized resting Yonetani-type cytochrome c-oxidase followed spectrophotometrically reveals a relatively rapid initial phase the rate of which shows saturation behaviour with respect to [HCN] and secondary slower absorption changes to a first approximation independent of the ligand concentration. Oxidized cytochrome c greatly accelerates the initial phase of cyanide binding but does not affect significantly contribution or rate constant of the slow phase. The same effect is exerted by poly-L-lysine. Within a framework of a reaction mechanism assuming Cu2+B to be the initial HCN-binding site, cytochrome c3+ and other polycations are likely to bring about a conformational-change of cytochrome oxidase resulting in an increased affinity of Cu2+B for HCN. This could occur by virtue of loosening a bond between Cu2+B and one of its endogenous ligands facilitating displacement of the latter by HCN.
authors.affiliation: Institute of Experimental Physics, Slovac Acad. Sci., Kosice, Czechoslovakia.
authors.forename: A
authors.initials: A
authors.lastname: Musatov
authors.forename: A A
authors.initials: AA
authors.lastname: Konstantinov
mesh_terms: D000818:Animals; D002417:Cattle; D003574:Cytochrome c Group / Q000494:pharmacology*; D003576:Electron Transport Complex IV / Q000378:metabolism; D006856:Hydrogen Cyanide / Q000378:metabolism; D007700:Kinetics; D010084:Oxidation-Reduction; D011190:Potassium Cyanide / Q000378:metabolism / Q000494:pharmacology; D011487:Protein Conformation / Q000187:drug effects; D013053:Spectrophotometry
chemical_list: D003574:Cytochrome c Group; D006856:Hydrogen Cyanide; D003576:Electron Transport Complex IV; D011190:Potassium Cyanide