Members in the Bcl-2 family are critical regulators of apoptosis by either inhibiting or promoting cell death. Bcl-2 homology 3 (BH3) domain is a potent death domain. BH3 domain containing pro-apoptotic proteins, including Bad, Bax, Bid, Bik, Hrk, Nip3, and Bim, form a growing subclass of the Bcl-2 family. A novel BH3 domain containing protein was recently identified and designated Bnip3L, Bnip3alpha, and Nix (for Nip3-like protein X). Bnip3L/Bnip3alpha/Nix is a homolog of the E1B 19K/Bcl-2 binding and pro-apoptotic protein Bnip3. Overexpression of Bnip3L induces apoptosis. Bnip3L interacts with and overcomes suppresses by Bcl-2 and Bcl-xL. Bnip3L is localized in mitochondria. The messenger RNA of Bnip3L is ubiquitously expressed in human tissues. Bnip3L and Bnip3 form a new subfamily of the pro-apoptotic mitochondrial proteins.
