. "Reviewed: Heldin, CH, 2008-02-12 09:44:02"^^ . "Edited: Orlic-Milacic, Marija, 2011-08-25"^^ . "Authored: Castagnoli, L, 2006-10-10 13:09:34"^^ . "SOS1 is the guanine nucleotide exchange factor (GEF) for RAS. SOS1 activates RAS nucleotide exchange from the inactive form (bound to GDP) to an active form (bound to GTP)."^^ . . . . . . "SOS1-mediated nucleotide exchange of RAS (EGF:EGFR:SHC1:GRB2:SOS1)"^^ . . . . .