The Active Sites of the Native Cytochrome-c Oxidase from Bovine Heart Mitochondria: EXAFS-Spectroseopic Characterization of a Novel Homobinuciear Copper Center (Cu_A) and of the HeteroMnucIear Fe_(a3)-Cu_B Center

摘要

Cytochrome-c oxidase [E.C. 1. 9. 3.1] catalyzes the reduction of molecular oxygen to water in the respiratory chain and converts the redox energy to an electrochemical proton potential across the plasma or mitochondria! membrane. Owing to its imponantfunction, the metallcenzyme has been the subject of numerous investigations. The membrane-spanning protein is composed of 13 subunits ana contains in addition to two heme-A groups (Fe_3 and Fe_(a3)) two copper centers (Cu_A and Cu_3) as well as a zinc and a magnesium ion. While the Cu_A center has been shown to act as the primary electron acceptor, the catalytic reduction of oxygen takes place at the binuclear center Fe_(a3)-Cu_B.