Ubiquinol-cytochrome c reductase complex (Complex III)

The ubiquinol-cytochrome c reductase complex, commonly referred to as Complex III or the cytochrome bc1 complex, is a vital multi-subunit enzyme situated within the inner mitochondrial membrane [1][3]. It functions as a central component of the electron transport chain, facilitating the transfer of electrons from ubiquinol to cytochrome c through a process known as the Q-cycle [3]. This electron transfer is coupled with the translocation of protons across the mitochondrial membrane, contributing to the electrochemical gradient necessary for ATP synthesis via oxidative phosphorylation [1]. Beyond its fundamental role in cellular energy production, Complex III is a significant therapeutic target, particularly for antiprotozoal drugs like atovaquone, which exploits structural differences between host and parasite complexes to achieve selectivity [2]. Dysfunctions or mutations in this complex are linked to a variety of mitochondrial disorders, such as GRACILE syndrome and Leigh-like syndrome, characterized by impaired metabolic activity and systemic organ failure [4]. Furthermore, research into Complex III inhibitors continues in the context of oncology, where disrupting mitochondrial respiration may hinder the growth and survival of certain cancer cells [2]. Sources: [1] UniProt (P00156); [2] PubChem (Atovaquone); [3] Wikipedia (Complex III); [4] NIH StatPearls (Mitochondrial Diseases).

Other names

Cytochrome bc1 complexCoenzyme Q-cytochrome c reductasebc1 complexCytochrome c reductaseUbiquinone-cytochrome c oxidoreductase

Inhibition of the Q-cycle by binding to the ubiquinol oxidation (Qo) or ubiquinone reduction (Qi) sites, thereby blocking electron transfer from ubiquinol to cytochrome c and preventing the generation of a proton gradient for ATP production.