Protein Sh2 Domains Combined. Grb7 Novel Non-phosphorylated Motif

The Grb7(growth factor receptor-bound7) protein, a member of the Grb7protein family, is found to be overexpressed in such metastatic tumors as breast cancer, esophageal cancer, liver cancer, etc. The grb7gene, locating at chromosomal position17q12-q21, has been proved to be amplificated in upper gastrointestinal cancer in clinical investigation. There are three major functional regions in Grb7protein, and the src-homology2(SH2) domain in the C-terminus is reported to be mainly involved in Grb7signal pathways. Using the random peptide library, we identified a series of Grb7SH2domain binding-nonphosphorylated peptides in the yeast two-hybrid system. These peptides had conserved sequence of GIPT/K/N at the N-terminus and G/WD/IP at the C-terminal, and the region between the N-and C-terminus contains fifteen amino acids enriched with serines, threonines and prolines. The association between the nonphosphorylated peptides and the Grb7SH2domain occurs in vitro and ex vivo. When competing for binding with Grb7SH2domain in a complex, synthesized nonphosphorylated ligand showed similar affinity comparable to that of phosphorylated ligand in vitro. Such nonphosphorylated peptides may be useful for rational design of drugs targeted against cancers expressing high levels of Grb7protein.