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.
Highlights
Cloning andExpression of cDNA for a Human Enzyme That Hydrolyzes 8-Oxo-dGTP, a Mutagenic Substrate for DNA Synthesis*
8-Oxoguanine (8-oxo-7, 8-dihydroguanine) is produced in DNA, as well as innucleotide 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
We reported evidence for a novel mechanism that prevents replicational errors by degrading a potent mutagenic substrate for DNA synthesis ( 5 ) .This error-avoiding process is catalyzed by a protein encoded by the mutT gene of E. coli, mutations of which increase the occurrence of A:T to C:G transversions 100-10,000-fold over the wild type level [14, 31,35]
Summary
Cloning andExpression of cDNA for a Human Enzyme That Hydrolyzes 8-Oxo-dGTP, a Mutagenic Substrate for DNA Synthesis*. When the human cDNA was expressed in E. coli mutT- mutant cells, there was a significant amount of 8-oxo-dGTPase activity. In the present study,we purified a human 8-oxo-dGTPase to physical homogeneity, and, using data of the amino acid sequence analysis, we clonedcDNAfor the enzyme.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
