E3 ubiquitin-protein ligase XIAP (XIAP)

Multi-functional protein which modulates not just caspases and apoptosis, but also modulates inflammatory signaling and immunity, copper homeostasis, mitogenic kinase signaling, cell proliferation, in addition to cell invasion and metastasis. Directly bind to the active site pocket of CASP3 and CASP7 and obstructs substrate entry.

Inactivates CASP9 by keeping it in a monomeric, inactive state. Acts as an E3 ubiquitin-protein ligase regulating NF-kappa-B signaling and the target proteins for its E3 ubiquitin-protein ligase activity include: RIPK1, CASP3, CASP7, CASP8, CASP9, MAP3K2/MEKK2, DIABLO/SMAC, AIFM1, CCS and BIRC5/survivin.