Structural and functional analysis of the ARF1-ARFGAP complex reveals a role for coatomer in GTP hydrolysis.
The crystal structure of the complex of ARF1 GTPase bound to GDP and the catalytic domain of ARF GTPase-activating protein (ARFGAP) has been determined at 1.95 A resolution. The ARFGAP molecule binds to switch 2 and helix alpha3 to orient ARF1 residues for catalysis, but it supplies neither arginine nor other amino acid side chains to the GTPase active site. In the complex, the effector-binding region appears to be unobstructed, suggesting that ARFGAP could stimulate GTP hydrolysis while ARF1 maintains an interaction with its effector, the coatomer complex of COPI-coated vesicles. Biochemical experiments show that coatomer directly participates in the GTPase reaction, accelerating GTP hydrolysis a further 1000-fold in an ARFGAP-dependent manner. Thus, a tripartite complex controls the GTP hydrolysis reaction triggering disassembly of COPI vesicle coats.
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; D000595:Amino Acid Sequence; D000818:Animals; D001120:Arginine; D020756:Coatomer Protein; D020558:GTP Phosphohydrolases / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D020690:GTPase-Activating Proteins; D006160:Guanosine Triphosphate / Q000378:metabolism*; D006801:Humans; D006868:Hydrolysis; D008565:Membrane Proteins / Q000378:metabolism*; D008969:Molecular Sequence Data; D011487:Protein Conformation; D011506:Proteins / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D051381:Rats; D017386:Sequence Homology, Amino Acid; D013329:Structure-Activity Relationship; D020703:ras GTPase-Activating Proteins; D018631:ras Proteins / Q000737:chemistry / Q000378:metabolism*
D020756:Coatomer Protein; D020690:GTPase-Activating Proteins; D008565:Membrane Proteins; D011506:Proteins; D020703:ras GTPase-Activating Proteins; D006160:Guanosine Triphosphate; D001120:Arginine; D020558:GTP Phosphohydrolases; D019204:GTP-Binding Proteins; D020823:ADP-Ribosylation Factor 1; D020727:ADP-Ribosylation Factors; D018631:ras Proteins