Mitochondrial cytochrome bc₁ complex (Cytochrome bc₁ complex)

The mitochondrial cytochrome bc₁ complex (complex III) is an intrinsic membrane protein dimer consisting of several subunits, most notably cytochrome b, cytochrome c₁, and the Rieske iron-sulfur protein. It catalyzes the oxidation of ubiquinol and the reduction of cytochrome c via the Q-cycle mechanism, generating a proton gradient essential for mitochondrial ATP production. Dysfunction in this complex can result in mitochondrial myopathies and contributes to increased production of reactive oxygen species, which are implicated in aging and various diseases. The complex is a key therapeutic target, with several drugs and research inhibitors acting by binding its quinone sites and disrupting electron transfer. Structural studies reveal it functions as a dimer, with coordinated binding and electron transfer across subunits.

Other names

Electron transport complex IIIComplex IIIUbiquinol-cytochrome c reductaseCytochrome b-c₁ complexRespiratory chain complex III

Inhibition of electron transport by blocking quinone (ubiquinol) binding sites (Qo/Qi sites) or interfering with electron transfer; Disruption of the proton gradient, leading to impaired ATP synthesis