Cloning and expression of cDNA for a human enzyme that hydrolyzes 8-oxo-dGTP, a mutagenic substrate for DNA synthesis

J Biol Chem. 1993 Nov 5;268(31):23524-30.

Abstract

8-Oxoguanine (8-oxo-7, 8-dihydroguanine) is produced in DNA, as well as in nucleotide pools of cells, by active oxygen species normally formed during cellular metabolic processes. 8-Oxoguanine nucleotide can pair with cytosine and adenine nucleotides at almost equal efficiencies, and transversion mutation ensues. Human cells contain enzyme activity, which hydrolyzes 8-oxo-dGTP to 8-oxo-dGMP, and this enzyme is responsible for preventing misincorporation of 8-oxoguanine into DNA. We purified this particular human enzyme to physical homogeneity and determined a partial amino acid sequence. We then cloned the cDNA for human 8-oxo-dGTPase and examined its nucleotide sequence. The human protein comprises 156 amino acid residues and has some sequence homology with the Escherichia coli MutT protein, which has a distinct 8-oxo-dGTPase activity. When the human cDNA was expressed in E. coli mutT- mutant cells, there was a significant amount of 8-oxo-dGTPase activity. In such cells, the frequency of spontaneous mutation was greatly reduced. We propose that the human 8-oxo-dGTPase protects genetic information from the untoward effects of endogenous oxygen radicals.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Base Sequence
  • Cloning, Molecular
  • DNA Repair
  • DNA Repair Enzymes*
  • DNA, Complementary / genetics
  • Deoxyguanine Nucleotides / metabolism*
  • GTP Phosphohydrolases / genetics*
  • Humans
  • Molecular Sequence Data
  • Mutagens / metabolism*
  • Peptides / chemistry
  • Phosphoric Monoester Hydrolases / genetics*
  • Recombinant Proteins
  • Restriction Mapping
  • Sequence Alignment
  • Sequence Homology, Amino Acid
  • Substrate Specificity

Substances

  • DNA, Complementary
  • Deoxyguanine Nucleotides
  • Mutagens
  • Peptides
  • Recombinant Proteins
  • 8-oxodeoxyguanosine triphosphate
  • Phosphoric Monoester Hydrolases
  • GTP Phosphohydrolases
  • 8-oxodGTPase
  • DNA Repair Enzymes

Associated data

  • GENBANK/D16581