Structural features of cytochrome oxidase

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Abstract
This article tries to be a compact summary of some recent research on cytochrome c oxidase (EC 1.9.3.1), an important enzyme in membrane bioenergetics. Cytochrome oxidase is the terminal catalyst of the mitochondrial respiratory chain. It uses the electrons flowing through the chain to reduce oxygen molecules to water. Four electrons and four protons are consumed in the reduction of O2 to two molecules of water (Fig. 1). Cytochrome oxidase contains four redoxactive metal centres. Two of these are copper atoms, two haem A groups. These four centres are employed in the dioxygen-binding site and in the electron-transferring pathways from cytochrome c. The enzyme is also called cytochrome aa3, because the protein-bound haems are functionally and spectroscopically different.