Coenzyme Q - cytochrome c reductase
The
Coenzyme Q - cytochrome c reductase complex, sometimes called the
cytochrome bc1 complex, and at other times Complex III, is the third complex in the
electron transfer chain (
PDB 1KYO, EC 1.10.2.2). It is a transmembrane
lipoprotein, and it catalyzes the reduction of
cytochrome c by accepting reducing equivalents from
Coenzyme Q (CoQ):
- CoQH2+ 2 Fe+3-cytochrome c → CoQ + 2 Fe+2-cytochrome c
In the process, protons are translocated across the
mitochondrial membrane. Therefore, the bc
1 complex is a
proton pump.
Compared to the other major proton pumping subunits of the electron transport chain, the number of subunits found can be small, as small as three polypeptide chains. This number does increase, and as many as eleven subunits can be found in higher animals. The major prosthetic groups in the complex are a pair of cytochromes, the b cytochrome and the c1 cytochrome, and a two iron, two sulfur iron-sulfur cluster.
More information can be found on the Cytochrome bc1 complex page.