Members of the Ras superfamily of small GTP-binding proteins are critical mediators of diverse cell signaling pathways, including those leading to cell proliferation, cytoskeletal organization and secretion. The counter-conversion of the active GTP-bound form of these proteins to their inactive GDP-bound form is influenced by two types of regulatory proteins: those that alter the intrinsic GTPase activity of the GTP-binding proteins and those that alter the rate of GDP/GTP exchange. DIRAS1 (DIRAS family, GTP-binding Ras-like 1), also known as distinct subgroup of the Ras family member 1, RIG (Ras-related inhibitor of cell growth), small GTP-binding tumor suppressor 1 or GBTS1, is a 198 amino acid cell membrane protein expressed at high levels in brain and heart. DIRAS1 displays low GTPase activity and is encoded by a gene that maps to human chromosome 19p13.3.