Autophosphorylation of tyrosine residues are docking sites for many downstream effectors in EGFR signaling. SH2-containing phosphotyrosine-binding domains of adaptor proteins like GRB2 is one such example. GRB2 is constitutively associated with SOS, a guanine nucleotide exchange factor of Ras. GRB2 binding to phosphorylated EGFR results in the recruitment of SOS to the plasma membrane where it comes in proximity to Ras. This mechanism has been seen to be the model for Ras activation.
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