Dissecting the Role of W60 in Grb2: Conformational Changes and Implications for Monomer Structure

The adaptor protein Grb2 is widely involved in various carcinomas due to its crucial role in signalling pathways responsible for cell growth and proliferation. Tryptophans play a crucial role in Grb2 function, with W36 and W193 being essential for recognizing proline-rich motifs in SH3 domains, and W121 is critical for Grb2 dimerization, obstructing pY+3 interactions and enabling SH2 domain swapping, contributing to interactions with natural molecules and inhibitors. Recent studies identified two dynamically independent subdomains within the Grb2 SH2 domain. Subdomain I, containing W60, is the primary site for phosphotyrosine recognition, while subdomain II, where W121 is located, provides specificity by recognizing the pY+2 position in the pY-x-N motif. Despite W60’s involvement in the canonical dimerization interface, its role in Grb2 structure and stability remains unexplored. Here, we present the biophysical characterization of Grb2 W60A and demonstrate the importance of this tryptophan residue to stability of the dimer. The exclusion of the lateral chain induces the monomerization of the protein in a flexible and elongated conformation, raising the question of how the interactions occurring in this subdomain can modulate the stability and dynamics of the protein, directly impacting its function within biological systems.