 Grb2 (or the Grb2/Sos complex) is recruited to the membrane by the Grb2 SH2 domain binding to activated PDGFR-bound SHP2 (also known as PTPN11, a cytosolic PTP), thereby allowing interaction with Ras and the exchange of GDP for GTP on Ras.Whereas the interaction between Grb2 and PDGFR occurs through interaction with the SHP2 protein, Grb2 instead binds to activated EGFR through Shc, another adaptor protein that forms a complex with many receptors via its PTB domain.Once activated, Ras interacts with several proteins, namely Raf.