Ubiquinol-cytochrome c reductase (Cytochrome bc1 complex) (Complex III)

The Ubiquinol-cytochrome c reductase (Cytochrome bc1 complex), also known as Complex III, is a multi-subunit enzyme essential for cellular respiration located in the inner mitochondrial membrane (Wikipedia: Cytochrome bc1 complex). It catalyzes the transfer of electrons from ubiquinol to cytochrome c through the Q-cycle mechanism, which is coupled to the translocation of protons across the membrane to generate a proton motive force (UniProt: P00156). This process is vital for ATP production via oxidative phosphorylation in almost all aerobic organisms. In medicine, the complex is a validated therapeutic target for treating parasitic infections, most notably malaria, where drugs like atovaquone bind to the ubiquinol-binding site (Qo) to disrupt the parasite's energy metabolism (PubMed: PMID 10572118). Mutations in the genes encoding its subunits, such as MT-CYB, are linked to mitochondrial encephalomyopathies and exercise intolerance in humans (NIH: MedlinePlus). Furthermore, the complex is a primary target for agricultural fungicides like strobilurins, which exploit structural differences between fungal and mammalian enzymes to achieve selectivity (PubChem: Azoxystrobin). Understanding the structural biology of this complex is crucial for developing next-generation inhibitors that can overcome emerging drug resistance in pathogens (PubMed: PMID 24352144).

Other names

bc1 complexCoenzyme Q-cytochrome c reductaseUbiquinone-cytochrome c oxidoreductaseComplex III

Inhibition of electron transfer by binding to the ubiquinol oxidation (Qo) or ubiquinone reduction (Qi) sites, thereby disrupting the proton motive force and ATP production (PubMed: PMID 10572118).