Fig. 1

The structure and composition of inhibitory of apoptosis proteins (IAPs) family members. a The three BIR domains characterize the members of the IAPs family, summarized in the list at the right corner. BIR1 does not contain the IAP binding motif (IBM), while BIRC2 and BIRC3 do contain the IBM and, thus, can interact with effector caspases and with Smac/Diablo. b Cellular IAPs (cIAPs) contain a caspase recruitment (CARD) domain in addition to the three BIR domains, the ubiquitin-conjugating (UBC) domain and the C-terminal Ring zinc-finger (RING) domain. The IBM groove is the one responsible for the binding of the N-terminal tetrapeptides