title: Resistance to hydrogen peroxide in Helicobacter pylori: role of catalase (KatA) and Fur, and functional analysis of a novel gene product designated 'KatA-associated protein', KapA (HP0874).
abstract: Helicobacter pylori infection elicits an aggressive inflammatory response that the bacterium is able to resist by virtue of its well-adapted antioxidant defence mechanisms. Catalase (KatA) appears to be a key enzyme in this resistance. Upstream of katA, a low-affinity ferric uptake regulator (Fur)-box has been identified. Downstream of katA, an ORF (HP0874) with no known function has also been identified. Non-polar isogenic mutants of katA, fur and HP0874 were constructed by allelic exchange. The impact of these mutations on the catalase activities and bacterial viability following exposure to hydrogen peroxide was studied. Concurrently, the effect of variation in the iron content of the media used to grow the cells was determined. The data showed that catalase-deficient isolates of H. pylori were hypersensitive to hydrogen peroxide, whereas wild-type cells could resist approximately approximately 100 mM hydrogen peroxide. Fur-deficient mutants and cells grown on low-iron-containing medium showed a distinct reduction in catalase activity and increased sensitivity to hydrogen peroxide. The data suggest a direct or indirect effect of Fur and iron on the activity of catalase. HP0874-deficient mutants showed no reduction in catalase activity but showed an increased sensitivity to hydrogen peroxide. That is, the protein encoded by HP0874 appears to have a role in resistance to hydrogen peroxide not directly related to catalase activity. This is the first report of a functional relationship of the product of this ORF. There is evidence of protein-protein interaction between KatA and the product encoded by HP0874, and the name 'KatA-associated protein' (KapA) is proposed.
authors.affiliation: Centre for Biomedical Research, Faculty of Sciences, University of Southern Queensland, Toowoomba, Australia 43502.|School of Microbiology and Immunology, University of New South Wales, Sydney, Australia 20521.
authors.forename: Andrew G
authors.initials: AG
authors.lastname: Harris
authors.affiliation: Centre for Biostructural and Biomolecular Research, University of Western Sydney, Campbelltown, Australia 25603.
authors.forename: Francis E
authors.initials: FE
authors.lastname: Hinds
authors.affiliation: School of Microbiology and Immunology, University of New South Wales, Sydney, Australia 20521.
authors.forename: Anthony G
authors.initials: AG
authors.lastname: Beckhouse
authors.affiliation: School of Microbiology and Immunology, University of New South Wales, Sydney, Australia 20521.
authors.forename: Tassia
authors.initials: T
authors.lastname: Kolesnikow
authors.affiliation: Centre for Biomedical Research, Faculty of Sciences, University of Southern Queensland, Toowoomba, Australia 43502.
authors.forename: Stuart L
authors.initials: SL
authors.lastname: Hazell
mesh_terms: D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism*; D002374:Catalase / Q000235:genetics / Q000378:metabolism*; D003470:Culture Media; D024881:Drug Resistance, Bacterial; D015964:Gene Expression Regulation, Bacterial; D018869:Heat-Shock Response; D016480:Helicobacter pylori / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics / Q000254:growth & development; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D007501:Iron / Q000378:metabolism; D009154:Mutation; D018384:Oxidative Stress; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D029681:Arabidopsis Proteins; D001426:Bacterial Proteins; D003470:Culture Media; C081231:KATA protein, Arabidopsis; D012097:Repressor Proteins; C068477:ferric uptake regulating proteins, bacterial; D006861:Hydrogen Peroxide; D007501:Iron; D002374:Catalase