Rap1A/B: ProductsRas-related Protein 1A (Rap1A) and Ras-related Protein 1B (Rap1B) are membrane-localized members of the Ras small GTPase superfamily of proteins. Rap1A and Rap1B are 184 amino acid (aa) propeptides that are processed into mature 181 aa proteins each with a predicted molecular mass of 21 kDa. Rap1A appears to play a vital role in the cardiovascular system where it regulates cell attachment, migration, and cell-cell junction formation. Rap1A counteracts the mitogenic functions of Ras and several reports suggest that it mediates the progression of multiple cancers where it may regulate metastasis. Rap1B has also been shown to participate in the organization of the vascular lumen by regulating endothelial cell polarity. It also plays a significant role in platelet function, where it mediates adhesion signaling.