Rap1 (Ras-proximate-1) is a small G protein in the Ras superfamily. Like all G proteins, Rap1 is activated when bound GDP is exchanged for GTP. Rap1 is targeted to lipid membranes by the covalent attachment of lipid moieties to its carboxyl terminus. Movement of Rap1 from endosomal membranes to the plasma membrane upon activation has been reported in several cell types including Jurkat T cells and megakaryocytes. On activation, Rap1 undergoes conformational changes that facilitate recruitment of a variety of effectors, triggering it's participation in integrin signaling, ERK activation, and others.