There are three distinct groups of Complex III inhibitors.
* Antimycin A binds to the Q site and inhibits the transfer of electrons in Complex III from heme b to oxidized Q (Qi site inhibitor).
* Myxothiazol and stigmatellin binds to the Q site and inhibits the transfer of electrons from reduced QH to the Rieske Iron sulfur protein. Myxothiazol and stigmatellin bind to distinct but overlapping pockets within the Q site.
** Myxothiazol binds nearer to cytochrome bL (hence termed a "proximal" inhibitor).
** Stigmatellin binds farther from heme bL and nearer the Rieske Iron sulfur protein, with which it strongly interacts.
Some have been commercialized as fungicides (the strobilurin derivatives, best known of which is azoxystrobin; QoI inhibitors) and as anti-malaria agents (atovaquone).
Also propylhexedrine inhibits cytochrome c reductase.