Complex III or quinol-cytochrome c reductase performs electron transfer coupled to proton pumping. It occurs as a symmetrical, tightly bound dimer (referred to as cIII2). This dimerisation occurs prior to the pre CIII complex formation, annotated as pre-CIII(2). Each monomer is composed of a catalytic core containing MT-CYB, CYC1 and UQCRFS1. An additional seven subunits are required for stability and/or correct assembly of the enzyme, but are not involved in the catalysis, but . e17 electron transport chain pathway PW:0000034 Pathway Ontology oxidative phosphorylation pathway PW:0001059 Pathway Ontology 30030361 PubMed Assembly of mammalian oxidative phosphorylation complexes I-V and supercomplexes. Essays Biochem 2018 Signes A Fernandez-Vizarra E