Enables GTP-dependent protein binding activity. Involved in several processes, including regulation of short-term neuronal synaptic plasticity; secretion by cell; and synaptic vesicle localization. Acts upstream of or within several processes, including chemical synaptic transmission; maintenance of presynaptic active zone structure; and synaptic vesicle maturation. Located in cytoplasmic vesicle; presynaptic active zone; and terminal bouton. Is anchored component of synaptic vesicle membrane. Is expressed in brain and inner ear. Orthologous to human RAB3A (RAB3A, member RAS oncogene family). [provided by Alliance of Genome Resources, Apr 2022]