Son of sevenless homolog 1 (Sos1) is a guanine nucleotide exchange factor (GEF) that directs the exchange of Ras-GDP to Ras-GTP by binding to SH3 domains of the growth factor receptor-bound protein 2 (Grb2), leading to the activation of ERK. Ras inhibitory peptide is a synthetic peptide that contains the sequence PVPPR, which corresponds to a region within human Sos1 that interacts with an SH3 domain of Grb2. It specifically blocks the interaction of the GEF with Grb2, preventing an interaction that is essential for Ras activation by receptor tyrosine kinases, including epidermal growth factor receptor.
