GTPase-activating protein (GAP) for the ADP ribosylation factor 1 (ARF1). Involved in membrane trafficking and /or vesicle transport. Promotes hydrolysis of the ARF1-bound GTP and thus, is required for the dissociation of coat proteins from Golgi-derived membranes and vesicles, a prerequisite for vesicle's fusion with target compartment. Probably regulates ARF1-mediated transport via its interaction with the KDELR proteins and TMED2. Overexpression induces the redistribution of the entire Golgi complex to the endoplasmic reticulum, as when ARF1 is deactivated. Its activity is stimulated by phosphoinosides and inhibited by phosphatidylcholine. Interacts with ARF1. Interacts with the COPI coat proteins, KDELR1 and TMED2. It is probably a component of the COPI coat protein complex. The interaction with TMED2 inhibits the GAP activity. Associates with the Golgi complex. Experimental confirmation may be lacking for some isoforms. Widely expressed. Highly expressed in brain and liver. The region downstream of Arf-GAP domain is essential to GAP activity in vivo. This region may be required for its targeting to Golgi membranes.