The
coenzyme Q : cytochrome c — oxidoreductase, sometimes called the
cytochrome bc1 complex, and at other times
complex III, is the third complex in the
electron transport chain , playing a critical role in biochemical generation of ATP (
oxidative phosphorylation). Complex III is a multisubunit transmembrane protein encoded by both the mitochondrial (
cytochrome b) and the nuclear genomes (all other subunits). Complex III is present in the
mitochondria of all animals and all aerobic eukaryotes and the inner membranes of most
eubacteria. Mutations in Complex III cause
exercise intolerance as well as multisystem disorders. The bc1
complex contains 11 subunits, 3 respiratory
subunits (cytochrome B,
cytochrome C1, Rieske protein), 2 core
proteins and 6 low-molecular
weight proteins.