Small GTP-binding protein which cycles between an inactive GDP-bound and an active GTP-bound form, and the rate of cycling is regulated by guanine nucleotide exchange factors (GEF) and GTPase-activating proteins (GAP). Required for normal cytokinesis and cilia signaling. Requires assistance from GTPase-activating proteins (GAPs) like RP2 and PDE6D, in order to cycle between inactive GDP-bound and active GTP-bound forms. Required for targeting proteins to the cilium, including myristoylated NPHP3 and prenylated INPP5E. Targets NPHP3 to the ciliary membrane by releasing myristoylated NPHP3 from UNC119B cargo adapter into the cilium (By similarity). Required for PKD1:PKD2 complex targeting from the trans-Golgi network to the cilium (By similarity). Found in a complex with ARL3, RP2 and UNC119 (or UNC119B); RP2 induces hydrolysis of GTP ARL3 in the complex, leading to the release of UNC119 (or UNC119B). Interacts with RP2; interaction is direct and stimulated with the activated GTP-bound form of ARL3. Interacts with SYS1. Interacts with ARL2BP; the GTP-bound form interacts with ARL2BP. Microtubule-associated protein. Does not interact with TBCC (By similarity). Interacts with RP2. Interacts with PDE6D; the interaction occurs specifically with the GTP-bound form of ARL3. Interacts with GGA1; the interaction recruits PKD1:PKD2 complex to trans-Golgi network and is required for ciliary targeting of PKD1:PKD2 complex (By similarity). Interacts with DNAAF9 (By similarity). Detected predominantly in the photoreceptor connecting cilium. Present on the mitotic spindle. Centrosome- associated throughout the cell cycle. Not detected to interphase microtubules (By similarity). Belongs to the small GTPase superfamily. Arf family.