Parasite cytochrome bc1 complex (cytochrome bc1 (or Cyt bc1))

The **parasite cytochrome bc1 complex** is a large, multi-subunit enzyme found in the mitochondrial inner membrane of eukaryotic pathogens such as Plasmodium (malaria), Toxoplasma, and many fungi. As a central part of the electron transport chain (complex III), it catalyzes the transfer of electrons from ubiquinol to cytochrome c, coupled with proton translocation across the mitochondrial membrane, thus generating the proton-motive force required for ATP synthesis. It is highly conserved but has enough sequence differences from the mammalian homolog to enable selective drug targeting. The complex has two main catalytic sites, Qo (quinol oxidation) and Qi (quinone reduction), both of which are exploited by drugs to disrupt parasite mitochondrial function and cause parasite death. Inhibition of this complex underpins the therapeutic effects of antimalarials such as atovaquone, but resistance caused by point mutations in the cytochrome b gene can develop, posing a continuing challenge for therapy[1][2][3][4][5][6].

Other names

Cytochrome bc1 complexCytochrome b–c1 complexComplex III (in electron transport chain context)Ubiquinol–cytochrome c oxidoreductase

Inhibition of electron transport by binding to quinol oxidation (Qo) or quinone reduction (Qi) sites, disrupting mitochondrial energy production and collapsing mitochondrial membrane potential, leading to parasite death