Stoichiometry and redox behaviour of metals in cytochrome-c oxidase.
The early observation of extra copper in preparations of cytochrome-c oxidase has recently lead to a renewed interest in its stoichiometry and possible redox function. In various, pure preparations (heme A contents close to the theoretical value of 9.79 nmol/mg protein for the 13-subunit bovine enzyme) protein-related metal stoichiometries of 3 Cu, 2 Fe, 1 Zn, 1 Mg/monomer with M(r) 204266 were determined. Despite the presence of five potential redox metal ions, reductive and reoxidative titrations indicate the presence of only four one-electron-accepting/donating species in the ligand-free enzyme. Participation of two copper ions in a binuclear copper site acting as one-electron acceptor may explain both the observed copper stoichiometry and the redox behaviour. The homology of the C-terminal sequence of subunit II with one of the copper-binding sites in nitrous-oxide reductases provides possible ligands for complexing two copper ions in a binuclear center.
Institut für Biochemie, Rheinisch-Westfälische Technische Hochschule Aachen, Germany.
G C
GC
Steffens
T
T
Soulimane
G
G
Wolff
G
G
Buse
D000595:Amino Acid Sequence; D000818:Animals; D002417:Cattle; D003300:Copper / Q000032:analysis; D003576:Electron Transport Complex IV / Q000032:analysis / Q000737:chemistry*; D008670:Metals / Q000032:analysis / Q000737:chemistry*; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D015032:Zinc / Q000032:analysis
D008670:Metals; D003300:Copper; D003576:Electron Transport Complex IV; D015032:Zinc