Inhibitor of apoptosis proteins (IAPs) contain conserved, unique N-terminal baculovirus IAP repeats (BIRs) and usually a C-terminal RING finger domain.
The BIR domain is essential for inhibitory activity and typically interacts with cysteine-containing aspartate-specific proteases (caspases as CASP3; MIM.600636) or with APAF1 (MIM.602233), which together with cytochrome C (MIM.123970) mediates activation of CASP9 (MIM.602234).
The RING finger domain sometimes enhances antiapoptotic activity but does not inhibit apoptosis alone.
References
Kim DK, Alvarado CS, Abramowsky CR, Gu L, Zhou M, Soe MM, Sullivan K, George B, Schemankewitz E, Findley HW. Expression of inhibitor-of-apoptosis protein (IAP) livin by neuroblastoma cells: correlation with prognostic factors and outcome. Pediatr Dev Pathol. 2005 Nov-Dec;8(6):621-9. PMID: 16328668