title: A peroxide/ascorbate-inducible catalase from Haemophilus influenzae is homologous to the Escherichia coli katE gene product.
abstract: Bacterial catalases are induced by exposure to peroxide (e.g., Escherichia coli katG) or entry into stationary phase (e.g., E. coli katE). To study regulatory systems in Haemophilus influenzae, we complemented an E. coli rpoS mutant, which is unable to induce katE in stationary phase, with a plasmid library of H. influenzae Rd- chromosomal DNA. Nineteen complementing clones with a catalase-positive phenotype were obtained and characterized after screening about 10(5) transformants. All carried the same structural gene for an H. influenzae catalase. The DNA sequence of this gene, called hktE, encodes a 508-amino-acid polypeptide with strong homology to eukaryotic catalases and E. coli katE. However, hktE is regulated like E. coli katG, with catalase activity increasing 10-fold and hktE mRNA levels increasing 4-fold upon exposure to ascorbic acid, which serves to generate hydrogen peroxide. Mutations in the known global regulatory genes of H. influenzae--crp, cya, and sxy--do not affect the inducibility of hktE. The hktE gene maps to a 225-kb segment of the H. influenzae chromosome in a region encoding resistance to spectinomycin.
authors.affiliation: Department of Medicine, Johns Hopkins Hospital, Baltimore, Maryland.
authors.forename: W R
authors.initials: WR
authors.lastname: Bishai
authors.forename: H O
authors.initials: HO
authors.lastname: Smith
authors.forename: G J
authors.initials: GJ
authors.lastname: Barcak
mesh_terms: D000595:Amino Acid Sequence; D001205:Ascorbic Acid / Q000494:pharmacology; D001483:Base Sequence; D002374:Catalase / Q000096:biosynthesis / Q000235:genetics*; D002874:Chromosome Mapping; D002876:Chromosomes, Bacterial; D004790:Enzyme Induction / Q000187:drug effects; D015964:Gene Expression Regulation, Bacterial; D015971:Gene Expression Regulation, Enzymologic; D015723:Gene Library; D005798:Genes, Bacterial / Q000235:genetics*; D006193:Haemophilus influenzae / Q000201:enzymology / Q000235:genetics*; D008969:Molecular Sequence Data; D010545:Peroxides / Q000494:pharmacology; D012641:Selection, Genetic; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D014170:Transformation, Genetic
chemical_list: D010545:Peroxides; D002374:Catalase; D001205:Ascorbic Acid