ADP-ribosylation factors (ARFs), are small guanine nucleotide-binding proteins that enhance the enzymatic activities of cholera toxin, and constitute one family of the RAS superfamily. ARFs are essential and ubiquitous in eukaryotes, as they are involved in vesicular transport and functioning via phospholipase D activation. ARF proteins play a role in membrane traffic and organelle integrity and are intimately tied to their reversible association with membranes and distinct interactions with membrane phospholipids. ARF1 is regulated by the binding and hydrolysis of GTP. Coatomer, or COPI, is a heptameric protein recruited to membranes by ARF1. Research demonstrates that guanine nucleotide exchange-activated ARF1, when located at the Golgi membrane, recruits and binds cytoplasmic COPI to the membranes.