Figure 3
From: Inhibitor of apoptosis proteins and their relatives: IAPs and other BIRPs
Mechanism of caspase inhibition by IAPs and its prevention by the IAP antagonist DIABLO/Smac. (a) The amino terminus of the p10 subunit of caspase 9, revealed following autoprocessing, interacts tightly within a groove of the BIR3 domain of XIAP. (b) The linker region upstream of the BIR2 domain of XIAP interacts tightly with the catalytic site of caspase 3 (and caspase 7; C indicates the catalytic cysteine residue), resulting in effective caspase inhibition. A less significant interaction of the amino terminus of the small subunit of caspase 3 within a groove of the BIR2 domain has been proposed. (c) The amino terminus of DIABLO (red) is similar to that of caspase 9 and competes for the exact same interaction site within the BIR3 domain. (d) A similar groove within the BIR2 domain of XIAP is believed to mediate interaction with DIABLO and provides a mechanism for DIABLO to remove caspase 3 from XIAP.