text: Survivin is a member of the IAP family of antiapoptotic proteins. It is shown to be conserved in function across evolution as homologues of the protein are found both in vertebrates and invertebrates. The first members of the IAPs identified were from the baculovirus IAPs, Cp-IAP and Op-IAP, which bind to and inhibit caspases as a mechanism that contributes to its efficient infection and replication cycle in the host. Later, five more human IAPs that included XIAP, c-IAPl, C-IAP2, NAIP, and survivin were discovered. Survivin, like the others, was discovered by its structural homology to IAP family of proteins in human B-cell lymphoma. The human IAPs, XIAP, c-IAPl, C-IAP2 have been shown to bind to caspase-3 and -7, which are the effector caspases in the signaling pathway of apoptosis. It is not known with absolute certainty though, how the IAPs inhibit apoptosis mechanistically at the molecular level.
  A common feature that is present in all IAPs in the presence of a BIR (Baculovirus IAP Repeat, a ~70 amino acid motif) in one to three copies. It was shown by Tamm et al. that knocking out BIR2 from XIAP was enough to cause a loss of function in terms of XIAPs ability to inhibit caspases. This gives the implication that it is within these BIR motifs that contains the anti-apoptotic function of these IAPs. Survivins one BIR domain shows a similar sequence compared to that of XIAPs BIR domains.