The small ADP ribosylation factor (Arf) GTP-binding proteins are major regulators of vesicle biogenesis in intracellular traffic.

Arf proteins cycle between inactive GDP-bound and active GTP-bound forms that bind selectively to effectors.

In GDP-bound Arf1 and Arf6, the interswitch is retracted and forms a pocket to which the N-terminal helix binds, the latter serving as a molecular hasp to maintain the inactive conformation.

ARFs regularly associate with two types of protein, those involved in catalyzing GTP/GDP exchange, and those that serve other functions.

The shape of the ARF molecule is dependent upon the form to which it is bound, allowing it to serve in a regulatory capacity.