The function of Ensembl gene identifier ENSG00000115904 (SOS1, SOS Ras/Rac guanine nucleotide exchange factor 1) is as follows. Promotes the exchange of Ras-bound GDP by GTP (PubMed:8493579). Probably by promoting Ras activation, regulates phosphorylation of MAP kinase MAPK3/ERK1 in response to EGF (PubMed:17339331). Catalytic component of a trimeric complex that participates in transduction of signals from Ras to Rac by promoting the Rac-specific guanine nucleotide exchange factor (GEF) activity (By similarity). {ECO:0000250|UniProtKB:Q62245, ECO:0000269|PubMed:17339331, ECO:0000269|PubMed:8493579}.