Mechanism of GTP hydrolysis by G-protein alpha subunits

Proc Natl Acad Sci U S A. 1994 Oct 11;91(21):9828-31. doi: 10.1073/pnas.91.21.9828.

Abstract

Hydrolysis of GTP by a variety of guanine nucleotide-binding proteins is a crucial step for regulation of these biological switches. Mutations that impair the GTPase activity of certain heterotrimeric signal-transducing G proteins or of p21ras cause tumors in man. A conserved glutamic residue in the alpha subunit of G proteins has been hypothesized to serve as a general base, thereby activating a water molecule for nucleophilic attack on GTP. The results of mutagenesis of this residue (Glu-207) in Gi alpha 1 refute this hypothesis. Based on the structure of the complex of Gi alpha 1 with GDP, Mg2+, and AlF-4, which appears to resemble the transition state for GTP hydrolysis, we believe that Gln-204 of Gi alpha 1, rather than Glu-207, supports catalysis of GTP hydrolysis by stabilization of the transition state.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Aluminum Compounds / metabolism
  • Amino Acid Sequence
  • Base Sequence
  • Conserved Sequence
  • DNA / chemistry
  • Escherichia coli
  • Fluorides / metabolism
  • GTP Phosphohydrolases / metabolism*
  • GTP-Binding Proteins / isolation & purification
  • GTP-Binding Proteins / metabolism*
  • Guanosine 5'-O-(3-Thiotriphosphate) / metabolism*
  • Guanosine Triphosphate / metabolism*
  • Humans
  • Hydrolysis
  • Kinetics
  • Macromolecular Substances
  • Magnesium / metabolism
  • Molecular Sequence Data
  • Mutagenesis, Site-Directed
  • Oligodeoxyribonucleotides
  • Phosphorus Radioisotopes
  • Proto-Oncogene Proteins p21(ras) / metabolism
  • Recombinant Proteins / isolation & purification
  • Recombinant Proteins / metabolism
  • Signal Transduction
  • Time Factors

Substances

  • Aluminum Compounds
  • Macromolecular Substances
  • Oligodeoxyribonucleotides
  • Phosphorus Radioisotopes
  • Recombinant Proteins
  • tetrafluoroaluminate
  • Guanosine 5'-O-(3-Thiotriphosphate)
  • Guanosine Triphosphate
  • DNA
  • GTP Phosphohydrolases
  • GTP-Binding Proteins
  • HRAS protein, human
  • Proto-Oncogene Proteins p21(ras)
  • Magnesium
  • Fluorides