Cilium-specific protein required to control the microtubule-based, ciliary axoneme structure. May act by maintaining the association between IFT subcomplexes A and B (By similarity). Monomer. Contains an incomplete active site due to the presence of a Gly residue in position 72 instead of a Gln, probably explaining the inability to hydrolyze GTP. Belongs to the small GTPase superfamily. Arf family.