The crystal structure of SMAC(DIABLO) at 2.2A resolution revealed that it homodimerized through an extensive hydrophobic interface and formed an elongated arch shaped quaternary structure (Chai J et al. 2000). Missense mutations that disrupt SMAC (DIABLO) dimeric interface, abrogated the XIAP‑neutralizing function of SMAC (DIABLO), suggesting that SMAC dimerization is essential for its pro‑apoptotic activity (Chai et al. 2000). SMAC (DIABLO) was also found to adopt a tetrameric assembly in solution (Mastrangelo E et al. 2015).