Arf1

ADP-ribosylation factor 1 (ARF1) is a small GTPase of the ARF family, encoded by the ARF1 gene in humans. It is highly conserved across eukaryotes and plays a central role in vesicular trafficking at the Golgi apparatus.

ARF1 cycles between an inactive GDP-bound state and an active GTP-bound state. In its GTP-bound form it associates with Golgi membranes, mediated by N-terminal myristoylation of glycine-2, which enables membrane insertion and a conformational change exposing an amphipathic helix. As a regulator of coat recruitment, ARF1-GTP recruits the coatomer complex COPI and other effector proteins to Golgi membranes, promoting cargo selection and vesicle budding for retrograde transport from the Golgi to the endoplasmic reticulum. ARF1 also participates in lipid signaling by activating phospholipase D and influencing phosphatidylinositol phosphate metabolism, contributing to membrane curvature and budding efficiency.

ARF1 activity is spatially and temporally controlled by guanine nucleotide exchange factors (GEFs), including GBF1 and the BIG family (BIG1, BIG2), which catalyze GDP-GTP exchange, and by GTPase-activating proteins (GAPs) such as ARFGAP1, which accelerate GTP hydrolysis and promote coat disassembly after vesicle formation.

ARF1 is roughly 180 amino acids in length and belongs to the small GTPase superfamily. Its activity is essential for normal Golgi function and secretory pathway traffic; disruption of ARF1 signaling perturbs protein trafficking and has been used to study membrane dynamics and coat assembly in various model systems.