Figure 1. Cellular inhibitor of apoptosis 1 (cIAP1) and cIAP2 have three baculoviral inhibitor of apoptosis repeat (BIR) domains.

BIR1 binds to tumour necrosis factor receptor-associated factor 1 (TRAF1) and TRAF2; BIR2 and BIR3 bind to Smac/Diablo and IAP antagonist compounds (IACs). The BIRs are followed by a ubiquitin-associated (UBA) domain that allows binding to ubiquitin [33]. This is followed by a caspase recruitment domain (CARD), but no proteins that bind to the CARD of IAPs have been identified. At the carboxy-terminus is a RING domain that allows dimerisation and confers ubiquitin E3 ligase activity.