Nomenclature for the human Arf family of GTP-binding proteins: ARF, ARL, and SAR proteins

Abstract

The Ras superfamily is comprised of at least four large families of regulatory guanosine triphosphate-binding proteins, including the Arfs. The Arf family includes three different groups of proteins: the Arfs, Arf-like (Arls), and SARs. Several Arf family members have been very highly conserved throughout eukaryotic evolution and have orthologues in evolutionally diverse species. The different means by which Arf family members have been identified have resulted in an inconsistent and confusing array of names. This confusion is further compounded by differences in nomenclature between different species. We propose a more consistent nomenclature for the human members of the Arf family that may also serve as a guide for nomenclature in other species.

Figure 1.

The structural “air de famille.” In Arfs, Arls, and SAR proteins, the interswitch toggles from an unusual retracted conformation in the GDP-bound form that is fastened by the NH₂-terminal helix to an exposed conformation in the GTP-bound form that is stabilized by the W/GG/R signature (shown here for ARF6-GDP and ARF6-GTP). This large conformational change, which involves a two-residue β-strand register shift in the core of the G domain, allows the nucleotide-binding site to detect remote interactions taking place at the NH₂ terminus (reproduced from Pasqualato et al., 2001 with permission).