Abstract
The GTPase-activating protein (GAP) stimulates the GTPase reaction of p21 by 5 orders of magnitude such that the kcat of the reaction is increased to 19 s-1. Mutations of residues in loop L1 (Gly-12 and Gly-13), in loop L2 (Thr-35 and Asp-38), and in loop L4 (Gln-61 and Glu-63) influence the reaction in different ways, but all of these mutant p21 proteins still form complexes with GAP. The C-terminal domain of the human GAP gene product, GAP334, which comprises residues 714 to 1047, is 20 times less active than full-length GAP on a molar basis and has a fourfold lower affinity. This finding indicates that the N terminus of GAP containing the SH2 domains modifies the interaction between the catalytic domain and p21.
MeSH terms
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Amino Acid Sequence
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Animals
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Antibodies, Monoclonal
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Baculoviridae / genetics
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Binding Sites
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Cell Line
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Chromosome Deletion
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Cloning, Molecular
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GTPase-Activating Proteins
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Genetic Vectors
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Guanosine Triphosphate / metabolism
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Insecta
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Kinetics
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Models, Structural
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Molecular Sequence Data
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Mutagenesis*
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PC12 Cells
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Protein Conformation
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Proteins / genetics*
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Proteins / isolation & purification
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Proteins / metabolism*
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Proto-Oncogene Proteins p21(ras) / genetics*
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Proto-Oncogene Proteins p21(ras) / isolation & purification
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Proto-Oncogene Proteins p21(ras) / metabolism*
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Recombinant Proteins / isolation & purification
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Recombinant Proteins / metabolism
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ras GTPase-Activating Proteins
Substances
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Antibodies, Monoclonal
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GTPase-Activating Proteins
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Proteins
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Recombinant Proteins
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ras GTPase-Activating Proteins
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Guanosine Triphosphate
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Proto-Oncogene Proteins p21(ras)