An antagonist of Bcl-2 family members containing four Bcl-2 homology domains, including Bcl-2, Bcl-W, Bcl-xL, and Mcl-1 (Kd ~500 nM); prevents interaction of these pro-survival proteins with Bax or Bak, inducing apoptosis; also induces autophagy in mouse embryo fibroblasts and in HeLa cell