This gene encodes a protein that belongs to a family of apoptotic suppressor proteins. Members of this family share a conserved motif termed, baculovirus IAP repeat, which is necessary for their anti-apoptotic function. This protein functions through binding to tumor necrosis factor receptor-associated factors TRAF1 and TRAF2 and inhibits apoptosis induced by menadione, a potent inducer of free radicals, and interleukin 1-beta converting enzyme. This protein also inhibits at least two members of the caspase family of cell-death proteases, caspase-3 and caspase-7. Mutations in this gene are the cause of X-linked lymphoproliferative syndrome. Alternate splicing results in multiple transcript variants. Pseudogenes of this gene are found on chromosomes 2 and 11.[provided by RefSeq, Feb 2011],disease:Defects in XIAP are the cause of lymphoproliferative syndrome X-linked type 2 (XLP2) [MIM:300635]. XLP is a rare immunodeficiency characterized by extreme susceptibility to infection with Epstein-Barr virus (EBV). Symptoms include severe or fatal mononucleosis, acquired hypogammaglobulinemia, pancytopenia and malignant lymphoma.,domain:The first BIR domain is involved in interaction with MAP3K7IP1 and is important for dimerization. The second BIR domain is sufficient to inhibit caspase-3 and caspase-7, while the third BIR is involved in caspase-9 inhibition. The interactions with SMAC and PRSS25 are mediated by the second and third BIR domains.,function:Apoptotic suppressor. Has E3 ubiquitin-protein ligase activity. Mediates the proteasomal degradation of target proteins, such as caspase-3, SMAC or AIFM1. Inhibitor of caspase-3, -7 and -9. Mediates activation of MAP3K7/TAK1, leading to the activation of NF-kappa-B.,online information:XIAP mutation db,PTM:Phosphorylation by PKB/AKT protects XIAP against ubiquitination and protects the protein against proteasomal degradation.,PTM:Ubiquitinated and degraded by the proteasome in apoptotic cells.,similarity:Belongs to the IAP family.,similarity:Contains 1 RING-type zinc finger.,similarity:Contains 3 BIR repeats.,subunit:Monomer, and homodimer. Interacts with SMAC and with PRSS25; these interactions inhibit apoptotic suppressor activity. Interacts with MAP3K7IP1 and AIFM1. Interaction with SMAC hinders binding of MAP3K7IP1 and AIFM1. Interacts with TCF25.,tissue specificity:Ubiquitous, except peripheral blood leukocytes.,