The BH3-only proteins comprise a subfamily of proapoptotic
Bcl-2 proteins (Huang and Strasser, 2000). As
their name indicates, BH3-only proteins share sequence homology
with the other Bcl-2 family members only within
the short amphipathic -helical BH3-domain, which serves
as the critical death domain, and are otherwise unrelated in
their sequence and structure to the Bcl-2 proteins. BH3-only
proteins are essential mediators of apoptosis by transducing
apoptotic signals to the central cell death machinery at the
mitochondria. The expression and activation of BH3-only
proteins is regulated in a tissue- and stimulus-specific manner