title: Differential regulation of amidase- and formamidase-mediated ammonia production by the Helicobacter pylori fur repressor.
abstract: The production of high levels of ammonia allows the human gastric pathogen Helicobacter pylori to survive the acidic conditions in the human stomach. H. pylori produces ammonia through urease-mediated degradation of urea, but it is also able to convert a range of amide substrates into ammonia via its AmiE amidase and AmiF formamidase enzymes. Here data are provided that demonstrate that the iron-responsive regulatory protein Fur directly and indirectly regulates the activity of the two H. pylori amidases. In contrast to other amidase-positive bacteria, amidase and formamidase enzyme activities were not induced by medium supplementation with their respective substrates, acrylamide and formamide. AmiE protein expression and amidase enzyme activity were iron-repressed in H. pylori 26695 but constitutive in the isogenic fur mutant. This regulation was mediated at the transcriptional level via the binding of Fur to the amiE promoter region. In contrast, formamidase enzyme activity was not iron-repressed but was significantly higher in the fur mutant. This effect was not mediated at the transcriptional level, and Fur did not bind to the amiF promoter region. These roles of Fur in regulation of the H. pylori amidases suggest that the H. pylori Fur regulator may have acquired extra functions to compensate for the absence of other regulatory systems.
authors.affiliation: Department of Gastroenterology and Hepatology, Erasmus MC University Medical Center Rotterdam, 3015 GD Rotterdam, The Netherlands. a.h.m.vanvliet@erasmusmc.nl
authors.forename: Arnoud H M
authors.initials: AH
authors.lastname: van Vliet
authors.forename: Jeroen
authors.initials: J
authors.lastname: Stoof
authors.forename: Sophie W
authors.initials: SW
authors.lastname: Poppelaars
authors.forename: Stefan
authors.initials: S
authors.lastname: Bereswill
authors.forename: Georg
authors.initials: G
authors.lastname: Homuth
authors.forename: Manfred
authors.initials: M
authors.lastname: Kist
authors.forename: Ernst J
authors.initials: EJ
authors.lastname: Kuipers
authors.forename: Johannes G
authors.initials: JG
authors.lastname: Kusters
mesh_terms: D000581:Amidohydrolases / Q000096:biosynthesis* / Q000378:metabolism; D000641:Ammonia / Q000378:metabolism*; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism*; D001483:Base Sequence; D004247:DNA / Q000378:metabolism; D005786:Gene Expression Regulation; D016480:Helicobacter pylori / Q000378:metabolism* / Q000472:pathogenicity; D006801:Humans; D007501:Iron / Q000494:pharmacology; D035925:Iron-Regulatory Proteins / Q000378:metabolism*; D008954:Models, Biological; D008969:Molecular Sequence Data; D009693:Nucleic Acid Hybridization; D010957:Plasmids / Q000378:metabolism; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D012313:RNA / Q000378:metabolism; D012097:Repressor Proteins / Q000737:chemistry / Q000378:metabolism*; D013379:Substrate Specificity; D014158:Transcription, Genetic; D014510:Urease / Q000737:chemistry
chemical_list: D001426:Bacterial Proteins; D035925:Iron-Regulatory Proteins; D012097:Repressor Proteins; C068477:ferric uptake regulating proteins, bacterial; D012313:RNA; D000641:Ammonia; D004247:DNA; D007501:Iron; D000581:Amidohydrolases; C019665:amidase; C101846:formamidase; D014510:Urease