GTPase-activating protein (GAP) for ADP ribosylation factor 1 (ARF1). Hydrolysis of ARF1-bound GTP may lead to dissociation of coatomer from Golgi-derived membranes to allow fusion with target membranes (By similarity). GAP activity stimulated by phosphatidylinositol 4,5-bisphosphate (PIP2). Also found on peripheral punctate structures likely to be endoplasmic reticulum-Golgi intermediate compartment.