Smac/Diablo is a 21 kDa mammalian mitochondrial protein that functions as a regulatory component during apoptosis. It promotes CASP9 activation bybinding to IAPs and removing their inhibitory activity. The inhibitor of apoptosis proteins(IAPs) regulate programmed cell death by inhibiting members of the caspase family ofenzymes. This interaction involves mainly the amino-terminal residues of Smac/Diablo with the BIR3 region of XIAP, supplemented with several other hydrophobic interactions between the helical structures of Smac/Diablo and other areas of BIR3. Smac/DIABLO is expressed in a variety of human and mouse tissues.
