BH3-only proteins - evolutionarily conserved proapoptotic Bcl-2 family members essential for initiating programmed cell death.

The BH3-only members of the Bcl-2 protein family are essential initiators of programmed cell death and are required for apoptosis induced by cytotoxic stimuli. These proteins have evolved to recognise distinct forms of cell stress. In response, they unleash the apoptotic cascade by inactivating the protective function of the pro-survival members of the Bcl-2 family and by activating the Bax/Bax-like pro-apoptotic family members.