Cytochrome bcc-aa3 oxidase subunit QcrB (QcrB)

Cytochrome bcc-aa3 oxidase subunit QcrB is the major redox-active subunit of the mycobacterial cytochrome bcc complex, part of the larger bcc-aa3 supercomplex crucial for aerobic respiration in mycobacteria such as *M. tuberculosis*. QcrB spans the membrane, binding two hemes (bH and bL), and constitutes the site where menaquinol oxidation initiates electron transfer to the respiratory chain, ultimately reducing molecular oxygen via the associated aa3-type oxidase domain. These reactions maintain the proton motive force for ATP synthesis. Selective inhibition of QcrB by small-molecule drugs (such as Q203) blocks this energy metabolism, leading to bactericidal effects. QcrB is structurally distinct from human mitochondrial complexes, making it an attractive target for antimicrobial drug development, particularly for drug-resistant tuberculosis

Other names

Cytochrome b subunit QcrBQcrB subunitMycobacterial cytochrome bCytochrome b bcc complex componentbc1 complex subunit QcrBbc complex subunit QcrB

Competitive inhibition of the Qp (menaquinol binding) site, preventing electron transfer to heme cofactors, halting respiratory ATP production, and thereby killing or stunting the proliferation of mycobacteria