Fig. 5.

On receipt of a death signal, the multidomain pro-apoptotic proteins Bax and Bak are oligomerized and activated, leading to mitochondrial outer membrane permeabilization. Once the mitochondrial membranes are permeabilized, cytochrome c is released into the cytoplasm and activates the caspase cascade, resulting in apoptosis. Anti-apoptotic Bcl-2 family proteins inhibits the release of cytochrome c by blocking activation of Bax and Bak. BH3-only proteins, which acts upstream of Bax and Bak, selectively binds with anti-apoptotic Bcl-2 family proteins to relieve their inhibition of Bax and Bad^98–101 (Used with permission from Abbott Laboratories).