Structural and functional studies of the Ras-associating and pleckstrin-homology domains of Grb10 and Grb14

Grb7, Grb10 and Grb14 are adapter proteins containing a Ras-associating (RA) domain, a pleckstrin-homology (PH) domain, a family-specific BPS (between PH and SH2) region, and a C-terminal Src-homology-2 domain. Previous structural studies showed that the Grb14 BPS region binds as a pseudosubstrate inhibitor in the tyrosine kinase domain of the insulin receptor to suppress insulin signaling. Here, we report the crystal structure of the RA and PH domains of Grb10 at 2.6 Å resolution. The structure reveals that these two domains, along with the intervening linker, form an integrated, dimeric structural unit. Biochemical studies demonstrated that Grb14 binds to activated Ras, which may serve as a timing mechanism for downregulation of insulin signaling. Our results illuminate not only membrane-recruitment mechanisms in Grb7-10-14, but also in MIG-10, Rap1-interacting adapter molecule, lamellipodin and Pico, proteins involved in actin-cytoskeleton rearrangement which share a structurally related RA-PH tandem unit.