Survival activity of Bcl-2 homologs Bcl-w and A1 only partially correlates with their ability to bind pro-apoptotic family members.

Certain Bcl-2 family members promote cell survival, whereas others promote apoptosis. To explore further how heterodimerization of opposing members affects survival activity, we have compared the abilities of the anti-apoptotic Bcl-w and A1 to bind to the pro-apoptotic Bax, Bak, Bad and Bik and to protect cells from their cytotoxic action. Bcl-w co-immunoprecipitated from cell lysates with Bax, Bak, Bad and Bik, but A1 bound only Bak and Bik.