Enables small GTPase binding activity. Involved in several processes, including chemical synaptic transmission; defecation; and positive regulation of cholinergic synaptic transmission. Located in axon and presynaptic active zone. Expressed in dorsal nerve cord; nerve ring; nervous system;
uv1; and ventral nerve cord. Is an ortholog of human RIMS1 (regulating synaptic membrane exocytosis 1).