Cytochrome c oxidase
The enzyme cytochrome c oxidase (PDB: 2OCC, EC 1.9.3.1) is a large transmembrane protein complex found in bacteria and the mitochondrion. It is the terminal electron acceptor in the electron transport chain in mitochondria and bacteria from four molecules of cytochrome c and converting molecular oxygen to two molecules of water. In the process, it translocates four protons, helping to establish a chemiosmotic potential that the ATP synthase then uses to synthesize ATP.
Summary reaction:
4 Fe2+-cytochrome c + 8 H+in + O2 → 4 Fe3+-cytochrome c + 2 H2O + 4 H+out
The complex is a large lipoprotein composed of several metal prosthetic sites and 13 protein subunits. In mammals, ten subunits are nuclear in origin and three are synthesized mitochondrially. The complex contains two cytochromes, the a and a3 cytochromes, and two copper centers, the CuA and CuB centers. In fact, the cytochrome a3 and CuB are a binuclear center that is the site of oxygen reduction. The mechanism of action of this large complex is still an active research topic.
Cyanide,sulfide and azide all bind to Cytochrome c Oxidase, thus inhibiting the protein from functioning which results in chemical suffocation.
External links
- The Cytochrome Oxidase home page
- Interactive Molecular model of cytochrome c oxidase (Requires MDL Chime)
- Calculated spatial positions of cytochrome c oxidases in membrane
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