SOLUTION STRUCTURE AND LIGAND-BINDING SITE OF THE CARBOXY-TERMINAL SH3 DOMAIN OF GRB2

Background: Growth factor receptor-bound protein 2 (GRB2) is an adapto r protein with three Src homology (SH) domains in the order SH3-SH2-SH 3. Both SH3 domains of GRB2 are necessary for interaction with the pro tein Son of sevenless (Sos), which acts as a Ras activator. Thus, GRB2 mediates signal transduction from growth factor receptors to Ras and is thought to be a key molecule in signal transduction. Results: The t hree-dimensional structure of the carboxy-terminal SH3 domain of GRB2 (GRB2 C-SH3) was determined by NMR spectroscopy. The SH3 structure con sists of six beta-strands arranged in two beta-sheets that are packed together perpendicularly with two additional beta-strands forming the third beta-sheet. GRB2 C-SHS is very similar to SH3 domains from other proteins. The binding site of the ligand peptide (VPP-PVPPRRR) derive d from the Sos protein was mapped on the GRB2 C-SHS domain indirectly using H-1 and N-15 chemical shift changes, and directly using several intermolecular nuclear Overhauser effects. Conclusions: Despite the st ructural similarity among the known SH3 domains, the sequence alignmen t and the secondary structure assignments differ. We therefore propose a standard description of the SH3 structures to facilitate comparison of individual SH3 domains, based on their three-dimensional structure s. The binding site of the ligand peptide on GRB2 C-SHS is in good agr eement with those found in other SH3 domains.