Discovery of thioether-bridged cyclic pentapeptides binding to Grb2-SH2 domain with high affinity

Abstract

Blocking the interaction between phosphotyrosine (pTyr)-containing activated receptors and the Src homology 2 (SH2) domain of the growth factor receptor-bound protein 2 (Grb 2) is considered to be an effective and non-cytotoxic strategy to develop new anti-proliferate agents due to its potential to shut down the Ras activation pathway. In this study, a series of phosphotyrosine containing cyclic pentapeptides were designed and synthesized based upon the phage library derived cyclopeptide, G1TE. A comprehensive SAR study was also carried out to develop potent Grb2-SH2 domain antagonists based upon this novel template. With both the peptidomimetic optimization of the amino acid side-chains and the constraint of the backbone conformation guided by molecular modeling, we developed several potent antagonists with low micromolar range binding affinity, such as cyclic peptide 15 with an K(d)=0.359microM, which is providing a novel template for the development of Grb2-SH2 domain antagonists as potential therapeutics for certain cancers.

Figure 1.

Molecular design of Grb2-SH2 domain antagonists based upon thioether-bridged cyclic peptide G1TE.

Figure 2.

General procedure for the synthesis of thioether and sulfoxide bridged cyclic pentapeptides.

Figure 3.

Synthetic route of cyclic pentapeptide 16.

Figure 4.

Docking poses of cyclic peptides 1 (A), 2 (B), 15 (C, R enantiomer) and 16 (D) with Grb2-SH2 domain (PDB ID 1TZE). Hydrogen bonds between ligands and protein are represented by yellow dot lines. For clarity, only polar hydrogen atoms are shown here.

Figure 5.

Conformation analyses of compounds 1, 15 and 16. Intramolecular hydrogen bonds are represented by yellow dot lines. For clarity, only polar hydrogen atoms are shown here.