RHEB is a recently discovered member of the Ras superfamily that may be involved in neural plasticity. This function is novel and not typically associated with the Ras proteins. RHEB gene is a member of the small GTPase superfamily and encodes a lipid-anchored, cell membrane protein with five repeats of the RAS-related GTP-binding region. RHEB is vital in regulation of growth and cell cycle progression due to its role in the insulin / TOR / S6K signaling pathway. The protein has GTPase activity and shuttles between a GDP-bound form and a GTP-bound form, and farnesylation of RHEB is required for this activity. Three pseudogenes have been mapped, two on chromosome 1 and one on chromosome 22.