Ubiquinol-cytochrome c reductase (Mitochondrial complex III) (Complex III)

Mitochondrial complex III, also known as the ubiquinol-cytochrome c reductase or the cytochrome bc1 complex, is a multi-subunit enzyme located in the inner mitochondrial membrane (UniProt P00156). It plays a central role in the electron transport chain by catalyzing the transfer of electrons from ubiquinol (reduced Coenzyme Q10) to cytochrome c, coupled with the translocation of protons across the membrane to generate a proton gradient for ATP synthesis (StatPearls, 2023). The complex contains two distinct binding sites for Coenzyme Q10: the Qo site (outer) and the Qi site (inner), which are critical for the Q-cycle mechanism (PubMed: 10629121). This complex is a significant therapeutic target, particularly for antiprotozoal drugs like atovaquone, which selectively inhibits the parasite's Qo site (PubMed: 10357835). Additionally, dysfunctions in complex III are linked to various mitochondrial diseases and are being explored as potential targets in cancer therapy to disrupt metabolic adaptation (PubMed: 30241594).

Other names

Cytochrome bc1 complexUbiquinol-cytochrome c oxidoreductaseCoenzyme Q-cytochrome c reductasebc1 complexMitochondrial complex III CoQ10 site

Inhibition of the Q-cycle by binding to the Qo (outer) or Qi (inner) ubiquinone-binding sites, preventing electron transfer from ubiquinol to cytochrome c (PubMed: 10629121).