Enables GTP binding activity. Involved in photoreceptor cell morphogenesis. Acts upstream of or within cilium assembly; flagellated sperm motility; and single fertilization. Located in sperm midpiece. Part of intraciliary transport particle B. Is expressed in several structures, including eye; genitourinary system; gut; nervous system; and respiratory system. Orthologous to several human genes including RABL2B (RAB, member of RAS oncogene family like 2B). [provided by Alliance of Genome Resources, Apr 2022]