Binding of a dimeric SMAC (DIABLO) N‑terminal peptide with the BIR2 domain of XIAP effectively antagonizes inhibition of caspase‑3 by XIAP (Wu G et al. 2000; Chai J et al. 2000). SMAC (DIABLO) interacts with the BIR3 and then BIR2 domains of XIAP sequentially, and such dynamic interaction cooperatively neutralizes inhibition of caspase‑3 by the linker region of XIAP (Gao Z et al. 2007).