1. A novel 3-methyladenine DNA glycosylase from Helicobacter pylori defines a new class within the endonuclease III family of base excision repair glycosylases.
- Author
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O'Rourke EJ, Chevalier C, Boiteux S, Labigne A, Ielpi L, and Radicella JP
- Subjects
- Amino Acid Motifs, Amino Acid Sequence, Binding Sites, Blotting, Western, Chromatography, High Pressure Liquid, DNA Adducts metabolism, DNA Glycosylases, Dose-Response Relationship, Drug, Electrophoresis, Polyacrylamide Gel, Endodeoxyribonucleases classification, Enzyme Induction, Lysine chemistry, Methyl Methanesulfonate pharmacology, Methylnitronitrosoguanidine pharmacology, Molecular Sequence Data, Mutagenesis, N-Glycosyl Hydrolases genetics, Open Reading Frames, Plasmids, Reverse Transcriptase Polymerase Chain Reaction, Sequence Homology, Amino Acid, Substrate Specificity, Transcription, Genetic, Bacterial Proteins, Deoxyribonuclease (Pyrimidine Dimer), Endodeoxyribonucleases chemistry, Escherichia coli Proteins, Helicobacter pylori enzymology, N-Glycosyl Hydrolases chemistry, N-Glycosyl Hydrolases classification
- Abstract
The cloning, purification, and characterization of MagIII, a 3-methyladenine DNA glycosylase from Helicobacter pylori, is presented in this paper. Sequence analysis of the genome of this pathogen failed to identify open reading frames potentially coding for proteins with a 3-methyladenine DNA glycosylase activity. The putative product of the HP602 open reading frame, reported as an endonuclease III, shares extensive amino acid sequence homology with some bacterial members of this family and has the canonic active site helix-hairpin-helix-GPD motif. Surprisingly, this predicted H. pylori endonuclease III encodes a 25,220-Da protein able to release 3-methyladenine, but not oxidized bases, from modified DNA. MagIII has no abasic site lyase activity and displays the substrate specificity of the 3-methyladenine-DNA glycosylase type I of Escherichia coli (Tag) because it is not able to recognize 7-methylguanine or hypoxanthine as substrates. The expression of the magIII open reading frame in null 3-methyladenine glycosylase E. coli (tag alkA) restores to this mutant partial resistance to alkylating agents. MagIII-deficient H. pylori cells show an alkylation-sensitive phenotype. H. pylori wild type cells exposed to alkylating agents present an adaptive response by inducing the expression of magIII. MagIII is thus a novel bacterial member of the endonuclease III family, which displays biochemical properties not described for any of the members of this group until now.
- Published
- 2000
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