Structural basis for activation of ARF GTPase: mechanisms of guanine nucleotide exchange and GTP-myristoyl switching.
Ras-related GTPases are positively regulated by guanine nucleotide exchange factors (GEFs) that promote the exchange of GDP for GTP. The crystal structure of the Sec7 domain GEF bound to nucleotide-free ARF1 GTPase has been determined at 2.8 A resolution and the structure of ARF1 in the GTP-analog form determined at 1.6 A resolution. The Sec7 domain binds to the switch regions of ARF1 and inserts residues directly into the GTPase active site. The interaction leaves the purine-binding site intact but perturbs the Mg2+ and phosphate groups to promote the dissociation of guanine nucleotides. The structure of ARF1 in the GTP-analog form closely resembles Ras, revealing a substantial rearrangement from the GDP conformation. The transition controls the exposure of the myristoylated N terminus, explaining how ARF GTPases couple the GDP-GTP conformational switch to membrane binding.
Goldberg
J
J
Cellular Biochemistry and Biophysics Program Memorial Sloan-Kettering Cancer Center, New York, New York 10021, USA. jonathan@ximpact4.ski.mskcc.org
D020823:ADP-Ribosylation Factor 1; D020727:ADP-Ribosylation Factors; D001665:Binding Sites / Q000502:physiology; D003461:Crystallography; D005656:Fungal Proteins / Q000737:chemistry / Q000378:metabolism; D020558:GTP Phosphohydrolases / Q000737:chemistry* / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000737:chemistry* / Q000378:metabolism*; D020662:Guanine Nucleotide Exchange Factors; D006160:Guanosine Triphosphate / Q000378:metabolism*; D008969:Molecular Sequence Data; D019814:Myristic Acid / Q000378:metabolism*; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D015003:Yeasts / Q000737:chemistry / Q000378:metabolism
D005656:Fungal Proteins; D020662:Guanine Nucleotide Exchange Factors; C066755:Sec7 guanine nucleotide exchange factors; D019814:Myristic Acid; D006160:Guanosine Triphosphate; D020558:GTP Phosphohydrolases; D019204:GTP-Binding Proteins; D020823:ADP-Ribosylation Factor 1; D020727:ADP-Ribosylation Factors