Smac/DIABLO promotes apoptosis by
XIAP is a potent inhibitor of caspases-3, -7 and -9. The mitochondrial protein Smac/DIABLO, released during MOMP, binds XIAP and neutralizes its inhibitory activity, thereby facilitating full activation of the caspase cascade. This dual control—release of both cytochrome c and Smac—ensures robust commitment to apoptosis once mitochondria are permeabilized. Careful
Ref: NCERT Biology Class 11–12 Alberts et al Molecular Biology of the Cell Lodish et al, Molecular Cell Biology Cooper & Hausman, The Cell Abbas et al., Cellular and Molecular Immunology (for immunology sections)
