The inhibitory binding site(s) of Zn2+ in cytochrome c oxidase

EXAFS analysis of Zn binding site(s) in bovine-heart cytochrome c oxidase and characterization of the inhibitory effect of internal zinc on respiratory activity and proton pumping of the liposome reconstituted oxidase are presented. EXAFS identifies tetrahedral coordination site(s) for Zn2+ with two N-histidine imidazoles, one N-histidine imidazol or N-lysine and one O–COOH (glutamate or aspartate), possibly located at the entry site of the proton conducting D pathway in the oxidase and involved in inhibition of the oxygen reduction catalysis and proton pumping by internally trapped zinc.