SOS1 activates H-Ras Authored: Ray, KP, 2010-05-17 Edited: Jupe, S, 2010-08-06 Pubmed17496910 Pubmed8493579 Reactome Database ID Release 43508236 Reactome, http://www.reactome.org ReactomeREACT_23928 Recruitment of Sos1 to the receptor complex brings it into contact with membrane-associated Ras-GDP. Interactions with Ras modulate Sos1 activity in a two-step manner (McKay & Morrison, 2007). Sos1 acts as a guanine exchange factor for Ras (Chardin et al. 1993), activating the Ras-Raf-MAPK pathway. Reviewed: Dooms, H, 2011-03-17 Reviewed: Villarino, A, 2011-02-11 HRAS:GTP HRAS:GDP