Mutational and kinetic analyses of the GTPase-activating protein (GAP)-p21 interaction: the C-terminal domain of GAP is not sufficient for full activity

Mol Cell Biol. 1992 May;12(5):2050-6. doi: 10.1128/mcb.12.5.2050-2056.1992.


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

  • Amino Acid Sequence
  • Animals
  • Antibodies, Monoclonal
  • Baculoviridae / genetics
  • Binding Sites
  • Cell Line
  • Chromosome Deletion
  • Cloning, Molecular
  • GTPase-Activating Proteins
  • Genetic Vectors
  • Guanosine Triphosphate / metabolism
  • Insecta
  • Kinetics
  • Models, Structural
  • Molecular Sequence Data
  • Mutagenesis*
  • PC12 Cells
  • Protein Conformation
  • Proteins / genetics*
  • Proteins / isolation & purification
  • Proteins / metabolism*
  • Proto-Oncogene Proteins p21(ras) / genetics*
  • Proto-Oncogene Proteins p21(ras) / isolation & purification
  • Proto-Oncogene Proteins p21(ras) / metabolism*
  • Recombinant Proteins / isolation & purification
  • Recombinant Proteins / metabolism
  • ras GTPase-Activating Proteins


  • Antibodies, Monoclonal
  • GTPase-Activating Proteins
  • Proteins
  • Recombinant Proteins
  • ras GTPase-Activating Proteins
  • Guanosine Triphosphate
  • Proto-Oncogene Proteins p21(ras)