Adapter protein that provides a critical link between cell surface growth factor receptors and the Ras signaling pathway. Associates with activated Tyr-phosphorylated EGF receptors and PDGF receptors via its SH2 domain. Also associates to other cellular Tyr-phosphorylated proteins such as SIT1, IRS1, SHC and LNK; probably via the concerted action of both its SH2 and SH3 domains. It also seems to interact with RAS in the signaling pathway leading to DNA synthesis. Binds to and translocates the guanine nucleotide exchange factors SOS (By similarity). Interacts with phosphorylated LAT2. Belongs to the GRB2/sem-5/DRK family.