Abstract
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.
MeSH terms
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ADP-Ribosylation Factor 1
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ADP-Ribosylation Factors
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Amino Acid Sequence
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Animals
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Arginine
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Coatomer Protein
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GTP Phosphohydrolases / metabolism*
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GTP-Binding Proteins / chemistry
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GTP-Binding Proteins / metabolism
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GTP-Binding Proteins / physiology*
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GTPase-Activating Proteins
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Guanosine Triphosphate / metabolism*
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Humans
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Hydrolysis
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Membrane Proteins / metabolism*
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Molecular Sequence Data
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Protein Conformation
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Proteins / chemistry
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Proteins / metabolism
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Proteins / physiology*
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Rats
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Sequence Homology, Amino Acid
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Structure-Activity Relationship
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ras GTPase-Activating Proteins
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ras Proteins / chemistry
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ras Proteins / metabolism*
Substances
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Coatomer Protein
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GTPase-Activating Proteins
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Membrane Proteins
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Proteins
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ras GTPase-Activating Proteins
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Guanosine Triphosphate
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Arginine
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GTP Phosphohydrolases
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GTP-Binding Proteins
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ADP-Ribosylation Factor 1
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ADP-Ribosylation Factors
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ras Proteins