Growth factor receptor-bound protein 2 (Grb2),
also known as Ash protein, is a 24 kDa protein that contains a
central Src homology (SH2) domain flanked by two SH3 domains. Grb2
is believed to be a regulatory subunit of signaling molecules whose
activity is modulated by receptor binding. Grb2 associates with
activated (tyrosine phosphorylated) EGFR and PDGFR via its SH2
domain as well as IRS1, SHC, and LNK through SH2 and SH3 domains.
The SH3 domain binds to SOS, a guanine nucleotide exchange factor
for Ras proteins. Endocytosis of activated EGFR requires the interaction
of Grb2 with the GTP binding protein dynamin, a factor essential
to the formation of endocytotic vesicle. It is ubiquitously expressed
and several isoforms are produced by alternative splicing. On SDS-PAGE,
Grb2 has an apparent molecular weight of 28 kDa.
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