title: A novel 3-methyladenine DNA glycosylase from Helicobacter pylori defines a new class within the endonuclease III family of base excision repair glycosylases.
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.
authors.affiliation: Département de Radiobiologie et Radiopathologie, Commissariat à l'Energie Atomique, UMR217 CEA/CNRS, BP6, 92265 Fontenay-aux-Roses, France.
authors.forename: E J
authors.initials: EJ
authors.lastname: O'Rourke
authors.forename: C
authors.initials: C
authors.lastname: Chevalier
authors.forename: S
authors.initials: S
authors.lastname: Boiteux
authors.forename: A
authors.initials: A
authors.lastname: Labigne
authors.forename: L
authors.initials: L
authors.lastname: Ielpi
authors.forename: J P
authors.initials: JP
authors.lastname: Radicella
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D001426:Bacterial Proteins; D001665:Binding Sites; D015153:Blotting, Western; D002851:Chromatography, High Pressure Liquid; D018736:DNA Adducts / Q000378:metabolism; D045647:DNA Glycosylases; D043224:Deoxyribonuclease (Pyrimidine Dimer); D004305:Dose-Response Relationship, Drug; D004591:Electrophoresis, Polyacrylamide Gel; D004706:Endodeoxyribonucleases / Q000737:chemistry* / Q000145:classification; D004790:Enzyme Induction; D029968:Escherichia coli Proteins; D016480:Helicobacter pylori / Q000201:enzymology*; D008239:Lysine / Q000737:chemistry; D008741:Methyl Methanesulfonate / Q000494:pharmacology; D008769:Methylnitronitrosoguanidine / Q000494:pharmacology; D008969:Molecular Sequence Data; D016296:Mutagenesis; D009699:N-Glycosyl Hydrolases / Q000737:chemistry* / Q000145:classification* / Q000235:genetics; D016366:Open Reading Frames; D010957:Plasmids; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity; D014158:Transcription, Genetic
chemical_list: D001426:Bacterial Proteins; D018736:DNA Adducts; D029968:Escherichia coli Proteins; D008769:Methylnitronitrosoguanidine; D008741:Methyl Methanesulfonate; D004706:Endodeoxyribonucleases; D043224:Deoxyribonuclease (Pyrimidine Dimer); C106403:NTH protein, E coli; D045647:DNA Glycosylases; C411653:DNA-3-methyladenine glycosidase MagIII, Helicobacter pylori; D009699:N-Glycosyl Hydrolases; D008239:Lysine