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. Author manuscript; available in PMC: 2013 Oct 1.
Published in final edited form as: Biopolymers. 2012;98(5):451–465. doi: 10.1002/bip.22080

Figure 1.

Figure 1

Interactions required for inhibition of caspase-9 clustered in the α5 helix are recapitulated in synthetic peptide inhibitors. (A) Structure of a caspase-9 monomer (purple) bound to XIAP-BIR3 (blue) observed in PDB 1NW9 (upper panel). A structural zinc (red sphere) is observed in XIAP-BIR3. The exosite is marked with a circle. The boxed region is highlighted in the lower panel. Hydrogen bonds (black dotted lines) between caspase-9 monomer and the α5 helix from XIAP-BIR3 provides recognition specificity to the complex. These interactions are recapitulated in the native peptides. (B) Specific interactions observed in the structure of caspase-9 bound to XIAP-BIR3 and those present in the three classes of designs are listed. (C) Modeled interactions of designed peptides based on an aPP scaffold (yellow) were designed to mimic the interactions between caspase-9 (purple) and the α5 helix. The polyproline helix labeled in the upper panel, has been removed from the lower panel for clarity. (D) Modeled interactions of α5-derived peptides stabilized by aliphatic staples (green) with caspase-9 (purple). Figures were drawn with PyMol73.