Cytochrome b (CYTB) (CYTB)

Cytochrome b is a critical transmembrane protein component of the mitochondrial cytochrome bc1 complex (Complex III), which is essential for the survival of various protozoan parasites, most notably Plasmodium falciparum (UniProt: Q02768) [1]. It functions as an oxidoreductase within the electron transport chain, facilitating the transfer of electrons from ubiquinol to cytochrome c while pumping protons across the inner mitochondrial membrane to maintain the membrane potential [2]. In parasites like Plasmodium, this process is uniquely vital because the electron transport chain provides the oxidized ubiquinone required by dihydroorotate dehydrogenase (DHODH) for de novo pyrimidine biosynthesis [3]. Since these parasites cannot salvage pyrimidines from the host, inhibition of cytochrome b leads to a cessation of DNA synthesis and parasite death [2]. The drug atovaquone is a potent inhibitor that targets the ubiquinol oxidation (Qo) site of the parasite's cytochrome b [4]. However, the therapeutic efficacy of such inhibitors is frequently compromised by the rapid emergence of resistance, often resulting from single nucleotide polymorphisms in the mitochondrial cytochrome b gene [1, 4].

Other names

Mitochondrial cytochrome bUbiquinol-cytochrome c reductase cytochrome b subunitComplex III subunit 3Cytb

Inhibition of the ubiquinol oxidation (Qo) site of the cytochrome bc1 complex, disrupting the mitochondrial electron transport chain and preventing the regeneration of ubiquinone required for pyrimidine biosynthesis.