Structure of the N-terminal SH3 Domain of GRB2 Complexed with a Peptide from the Guanine Nucleotide Releasing Factor Sos

Src-homology 3 (SH3) domains mediate signal transduction by binding to proline-rich motifs in target proteins. We have determined the high-resolution NMR structure of the complex between the amino-terminal SH3 domain of GRB2 and a ten amino acid peptide derived from the guanine nucleotide releasing factor Sos. The NMR data show that the peptide adopts the conformation of a left-handed polyproline type II helix and interacts with three major sites on the SH3 domain. The orientation of the bound peptide is opposite to that of proline-rich peptides bound to the SH3 domains of Abl, Fyn and p85.