Cytochrome c oxidase binuclear heme a3-CuB center (COX BNC)

The Cytochrome c oxidase binuclear heme a3-CuB center is the primary catalytic site of Complex IV, the final enzyme in the mitochondrial respiratory electron transport chain (Source: Wikipedia, Cytochrome c oxidase). This site consists of a high-spin heme a3 iron and a copper ion (CuB), which together facilitate the four-electron reduction of molecular oxygen to water (Source: J Biol Chem. 2012;287(16):13448-13455). This process is vital for aerobic life, as it drives the proton gradient necessary for ATP synthesis (Source: UniProt P00395). The binuclear center is the specific target of lethal inhibitors such as cyanide, carbon monoxide, and hydrogen sulfide, which bind to the heme a3 iron and block oxygen binding, resulting in immediate cessation of cellular respiration (Source: StatPearls, Cyanide Toxicity). Clinically, dysfunction of this center is associated with mitochondrial encephalomyopathies like Leigh syndrome and is a focal point in the study of neurodegenerative diseases and ischemia-reperfusion injury (Source: NIH, Genetics Home Reference). Because of its central role in energy metabolism, the site is a critical marker for metabolic health and a key subject in toxicological research.

Other names

Heme a3-CuB centerBinuclear center of cytochrome c oxidaseComplex IV active siteCytochrome aa3 binuclear centerOxygen reduction site of Complex IV

Inhibitors bind to the heme a3 iron or the CuB center, competitively or non-competitively blocking the binding and reduction of molecular oxygen, thereby halting the electron transport chain and ATP production (Source: PubChem, Cyanide; StatPearls, Carbon Monoxide Toxicity).