GTP-binding protein that functions as an allosteric activator of the cholera toxin catalytic subunit, an ADP-ribosyltransferase. Involved in protein trafficking; may modulate vesicle budding and uncoating within the Golgi apparatus (By similarity). Interacts with PRKCABP. Interacts with PI4KB and NCS1/FREQ at the Golgi complex. Belongs to the small GTPase superfamily. Arf family.