Structure-Activity Studies in a Family of beta-Hairpin Protein Epitope Mimetic Inhibitors of the p53-HDM2 Protein-Protein Interaction.Fasan, R., Dias, R.L., Moehle, K., Zerbe, O., Obrecht, D., Mittl, P.R., Robinson, J.A.
(2006) Chembiochem 7: 515-526
- PubMed: 16511824
- DOI: 10.1002/cbic.200500452
- Primary Citation of Related Structures:
- PubMed Abstract:
Inhibitors of the interaction between the p53 tumor-suppressor protein and its natural human inhibitor HDM2 are attractive as potential anticancer agents. In earlier work we explored designing beta-hairpin peptidomimetics of the alpha-helical epitope ...
Inhibitors of the interaction between the p53 tumor-suppressor protein and its natural human inhibitor HDM2 are attractive as potential anticancer agents. In earlier work we explored designing beta-hairpin peptidomimetics of the alpha-helical epitope on p53 that would bind tightly to the p53-binding site on HDM2. The beta-hairpin is used as a scaffold to display energetically hot residues in an optimal array for interaction with HDM2. The initial lead beta-hairpin mimetic, with a weak inhibitory activity (IC(50)=125 microM), was optimized to afford cyclo-(L-Pro-Phe-Glu-6ClTrp-Leu-Asp-Trp-Glu-Phe-D-Pro) (where 6ClTrp=L-6-chlorotryptophan), which has an affinity almost 1,000 times higher (IC(50)=140 nM). In this work, insights into the origins of this affinity maturation based on structure-activity studies and an X-ray crystal structure of the inhibitor/HDM2(residues 17-125) complex at 1.4 A resolution are described. The crystal structure confirms the beta-hairpin conformation of the bound ligand, and also reveals that a significant component of the affinity increase arises through new aromatic/aromatic stacking interactions between side chains around the hairpin and groups on the surface of HDM2.
Institute of Organic Chemistry, University of Zürich, Winterthurerstrasse 190, 8057 Zürich, Switzerland.