Promotes cell death. Successfully competes for the binding to Bcl-X(L), Bcl-2 and Bcl-W, thereby affecting the level of heterodimerization of these proteins with BAX. Can reverse the death repressor activity of Bcl-X(L), but not that of Bcl-2 (By similarity). Appears to act as a link between growth factor receptor signaling and the apoptotic pathways. Forms heterodimers with the anti-apoptotic proteins, Bcl-X(L), Bcl-2 and Bcl-W. Also binds protein S100A10. The Ser-113/Ser-137 phosphorylated form binds 14-3-3 proteins. Interacts with AKT1 and PIM3 (By similarity). Interacts with HIF3A (via C-terminus domain); the interaction reduces the binding between BAD and BAX (By similarity). Interacts (via BH3 domain) with NOL3 (via CARD domain); preventing the association of BAD with BCL2 (PubMed:17998337). Interacts with GIMAP3/IAN4 and GIMAP5/IAN5 (By similarity). Colocalizes with HIF3A in the cytoplasm. Upon phosphorylation, locates to the cytoplasm. Expressed in all tissues tested, including brain, liver, spleen and heart. In the brain, restricted to epithelial cells of the choroid plexus. Isoform alpha is the more abundant form. Intact BH3 motif is required by BIK, BID, BAK, BAD and BAX for their pro-apoptotic activity and for their interaction with anti-apoptotic members of the Bcl-2 family. Phosphorylated at one or more of Ser-113, Ser-137, Ser-156 and Ser-171 in response to survival stimuli, which blocks its pro-apoptotic activity. Phosphorylation on Ser-137 or Ser-113 promotes heterodimerization with 14-3-3 proteins. This interaction then facilitates the phosphorylation at Ser-156, a site within the BH3 motif, leading to the release of Bcl-X(L) and the promotion of cell survival. Ser-137 is the major site of AKT/PKB phosphorylation, Ser-156 the major site of protein kinase A (CAPK) phosphorylation. Methylation at Arg-132 and Arg-134 by PRMT1 inhibits Akt-mediated phosphorylation at Ser-137. Belongs to the Bcl-2 family. The protein name 'Bcl2 antagonist of cell death' may be misleading. The protein antagonises Bcl2-mediated repression of cell death, hence it promotes apoptosis.