Intracellular vesicle trafficking and protein transport. Binds GTP and GDP and possesses intrinsic GTPase activity. Interacts (via C-terminus) with GDI1. Interacts with PUX8/SAY1. Expressed in roots and actively dividing cells. By abscisic acid (ABA), phosphate (Pi) deprivation, cold, sucrose, mannose, and water stress. Belongs to the small GTPase superfamily. Rab family.