Presence of Active Aliphatic Amidases in
            <i>Helicobacter</i>
            Species Able To Colonize the Stomach

Bury‐Moné, Stéphanie; Skouloubris, Stéphane; Dauga, Catherine; Thiberge, Jean‐Michel; Dailidiene, Daiva; Berg, Douglas E.; Labigne, Agnès; Reuse, Hilde De

doi:10.1128/iai.71.10.5613-5622.2003

Cited by 64 publications

(61 citation statements)

References 52 publications

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“…We hypothesize that enterohepatic Helicobacter species do not require high levels of urease activity in the rodent gut. The high levels of urease activity observed in gastric Helicobacter species (Bury-Mone et al, 2003;Scott et al, 2000) are likely to be an adaptation that allows them to thrive in the gastric environment, albeit at a high metabolic cost. Regulation of urease expression and activity will allow them to adapt to changes in acidity observed during fasting or feeding.…”

Section: Discussionmentioning

confidence: 99%

Differential regulation of urease activity in Helicobacter hepaticus and Helicobacter pylori

et al. 2005

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Helicobacter hepaticus is a pathogen of rodents, which causes diverse enteric and hepatic inflammatory diseases and malignancies. The urease enzyme is an important colonization factor of gastric Helicobacter species like Helicobacter pylori, but little is known about the role and regulation of urease in enterohepatic Helicobacter species. Here it is reported that urease activity of H. hepaticus does not contribute to acid resistance, and that it is nickel-responsive at the post-translational level. H. hepaticus strain ATCC 51449 did not grow or survive at pH 3?0, and supplementation with urea or NiCl 2 did not abrogate this acid sensitivity. Furthermore, urease enzyme activity of H. hepaticus was acid-independent, which contrasts with the acid-induced urease system of H. pylori. Nickel supplementation of Brucella medium resulted in a tenfold increase in urease activity in both H. hepaticus and H. pylori, but the maximum level of urease activity in H. hepaticus was still three-to fivefold lower when compared to H. pylori in the same conditions. The increase in urease activity of H. hepaticus was not associated with elevation of urease mRNA or protein levels. Inhibition of protein synthesis by chloramphenicol did not affect nickel-responsive induction of urease activity in H. hepaticus, and confirmed that nickel induction occurs at the post-translational level, probably by activation of preformed apo-enzyme. In conclusion, both the role of the urease enzyme and the regulation of urease activity differ between the enterohepatic pathogen H. hepaticus and the gastric pathogen H. pylori.

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Section: Discussionmentioning

confidence: 99%

Differential regulation of urease activity in Helicobacter hepaticus and Helicobacter pylori

et al. 2005

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“…Interestingly, both amiE (HP0924) and amiF (HP1238), two amidases carried in the H. pylori genome, were identified as having a phenotype in the NSH57 strain background but not in the NSH79 strain background. A previous study also found that amidase gene function is not required for colonization in the SS1 strain background (9).…”

Section: Vol 75 2007mentioning

confidence: 99%

Identification of Helicobacter pylori Genes That Contribute to Stomach Colonization

et al. 2007

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Chronic infection of the human stomach by Helicobacter pylori leads to a variety of pathological sequelae, including peptic ulcer and gastric cancer, resulting in significant human morbidity and mortality. Several genes have been implicated in disease related to H. pylori infection, including the vacuolating cytotoxin and the cag pathogenicity island. Other factors important for the establishment and maintenance of infection include urease enzyme production, motility, iron uptake, and stress response. We utilized a C57BL/6 mouse infection model to query a collection of 2,400 transposon mutants in two different bacterial strain backgrounds for H. pylori genetic loci contributing to colonization of the stomach. Microarray-based tracking of transposon mutants allowed us to monitor the behavior of transposon insertions in 758 different gene loci. Of the loci measured, 223 (29%) had a predicted colonization defect. These included previously described H. pylori virulence genes, genes implicated in virulence in other pathogenic bacteria, and 81 hypothetical proteins. We have retested 10 previously uncharacterized candidate colonization gene loci by making independent null alleles and have confirmed their colonization phenotypes by using competition experiments and by determining the dose required for 50% infection. Of the genetic loci retested, 60% have strain-specific colonization defects, while 40% have phenotypes in both strain backgrounds for infection, highlighting the profound effect of H. pylori strain variation on the pathogenic potential of this organism.Helicobacter pylori, a bacterial pathogen of the human stomach, infects an estimated 50% of the population worldwide. Infection by H. pylori causes gastritis initially and, if allowed to persist, can induce a range of pathologies. It is the causative agent of most peptic ulcers, and other serious outcomes such as atrophic gastritis, intestinal metaplasia, and gastric cancer are correlated with long-term infections. It is not yet known whether these outcomes are due to specific factors produced by the organism or whether they result from chronic inflammation due to efficient and persistent colonization of the gastric mucosa. Thus, colonization and persistence factors may themselves constitute virulence factors for this organism.

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“…coli strain MC1061 (29) was grown at 37°C in Luria broth (30) with 100 g/ml ampicillin or carbenicillin, 100 g/ml spectinomycin, or 20 g/ml kanamycin if appropriate. Transformation of H. pylori was carried out as described previously (31). Cells that had recombined the tag into the chromosome were selected by their resistance to kanamycin.…”

Section: Strains and Growth Conditionsmentioning

confidence: 99%

In Vivo Interactome of Helicobacter pylori Urease Revealed by Tandem Affinity Purification

Stingl

Schauer

Ecobichon

et al. 2008

Molecular & Cellular Proteomics

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In the human gastric bacterium Helicobacter pylori, two metalloenzymes, hydrogenase and urease, are essential for in vivo colonization, the latter being a major virulence factor. The UreA and UreB structural subunits of urease and UreG, one of the accessory proteins for Ni 2؉ incorporation into apourease, were taken as baits for tandem affinity purification. The method allows the purification of protein complexes under native conditions and physiological expression levels of the bait protein. Protein-protein interactions are operative at the majority of cellular processes; thus, their study gives valuable insight into proteomic and functional associations. Helicobacter pylori is a Gram-negative bacterium that is infecting the stomach of about half of the human population. It is responsible for the development of gastric pathologies such as gastritis, gastroduodenal ulcer, and adenocarcinoma (1). One remarkable feature of H. pylori is its capacity to persist (often during decades) and multiply in the hostile environment of the stomach. In H. pylori, urease is a major virulence factor and is essential for the resistance to acidity because of its capacity to hydrolyze urea into bicarbonate and ammonia (2), which results in pH homeostasis of the bacterium. The protein is an extremely active and highly regulated member of the nickel metalloenzyme family. Activation of urease, i.e. incorporation of nickel into the active site, requires urease-specific accessory proteins whose homologues have been extensively studied genetically and biochemically in Klebsiella pneumoniae (3)(4)(5)(6)(7)(8). It is still enigmatic why vast amounts of urease, up to 10% of the total protein, are produced, whereas only a minor active portion is sufficient for acid resistance (9). Furthermore the observation that urease is even indispensable for the colonization under neutral conditions (10) suggested additional essential functions for this central enzyme that remained unidentified.H. pylori possesses another nickel-containing enzyme, a [NiFe] hydrogenase, allowing this organism to utilize hydrogen as an energy source. Accordingly hydrogenase has been shown to be essential for H. pylori colonization in the mouse model (11). The assembly of the [NiFe] hydrogenase metal center located in the large hydrogenase subunit is partially understood and requires several proteins involved in the sequential delivery of iron before nickel (for a review, see Ref. 12). In addition, the [NiFe] hydrogenase possesses a small subunit containing [Fe-S] clusters. For the assembly of the latter no distinct biosynthetic pathway has been attributed so far, suggesting that the housekeeping [Fe-S] cluster assembly system might be involved (12). H. pylori is unique in that the maturation events of these two nickel-containing essential proteins are interconnected as H. pylori mutants deficient in one of the accessory proteins, HypA or HypB, involved in nickel insertion into hydrogenase, lack significant activation of urease (13).

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Presence of Active Aliphatic Amidases in Helicobacter Species Able To Colonize the Stomach

Cited by 64 publications

References 52 publications

Differential regulation of urease activity in Helicobacter hepaticus and Helicobacter pylori

Differential regulation of urease activity in Helicobacter hepaticus and Helicobacter pylori

Identification of Helicobacter pylori Genes That Contribute to Stomach Colonization

In Vivo Interactome of Helicobacter pylori Urease Revealed by Tandem Affinity Purification

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