Two lipid-packing sensor motifs contribute to the sensitivity of ArfGAP1 to membrane curvature

Biochemistry. 2007 Feb 20;46(7):1779-90. doi: 10.1021/bi062288w. Epub 2007 Jan 25.

Abstract

ArfGAP1 (Arf GTPase activating protein 1) controls the cycling of the COPI coat on Golgi membranes by catalyzing GTP hydrolysis in the small G protein Arf1. ArfGAP1 contains a central motif named ALPS (ArfGAP1 lipid-packing sensor) that adsorbs preferentially onto highly curved membranes. This motif allows coupling of the rate of GTP hydrolysis in Arf1 with membrane curvature induced by the COPI coat. Upon membrane adsorption, the ALPS motif folds into an amphipathic alpha-helix. This helix contrasts from a classical membrane-adsorbing helix in the abundance of S and T residues and the paucity of charged residues in its polar face. We show here that ArfGAP1 contains a second motif with similar physicochemical properties. This motif, ALPS2, also forms an amphipathic alpha-helix at the surface of small vesicles and contributes to the Golgi localization of ArfGAP1 in vivo. Using several quantitative assays, we determined the relative contribution of the two ALPS motifs in the recognition of liposomes of defined curvature and composition. Our results show that ALPS1 is the primary determinant of the interaction of ArfGAP1 with lipid membranes and that ALPS2 reinforces this interaction 40-fold. Furthermore, our results suggest that depending on the engagement of one or two functional ALPS motifs, ArfGAP1 can respond to a wide range of membrane curvature and can adapt to lipid membranes of various acyl chain compositions.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Motifs
  • Amino Acid Sequence
  • Animals
  • Cell Membrane / metabolism
  • Circular Dichroism
  • GTPase-Activating Proteins / chemistry*
  • GTPase-Activating Proteins / genetics
  • GTPase-Activating Proteins / metabolism
  • Golgi Apparatus / metabolism
  • Green Fluorescent Proteins / genetics
  • Green Fluorescent Proteins / metabolism
  • HeLa Cells
  • Humans
  • Liposomes / chemistry*
  • Microscopy, Fluorescence
  • Molecular Sequence Data
  • Mutation
  • Rats
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism
  • Spectrometry, Fluorescence

Substances

  • Arfgap1 protein, rat
  • GTPase-Activating Proteins
  • Liposomes
  • Recombinant Fusion Proteins
  • Green Fluorescent Proteins