Bcl-B (also called Bcl2-L-10) is a novel anti-apoptotic member of the Bcl-2 family. Bcl-B is closest in amino acid sequence homology to Boo protein. It contains four Bcl-2 homologs. Bcl-B mRNA is widely expressed in adult human tissues. The Bcl-B protein binds to Bcl-2, Bcl-X(L), and Bax but not Bak. Bcl-B suppresses apoptosis induced by Bax, but not by Bak.