Differential regulation of urease activity in Helicobacter hepaticus and Helicobacter pylori

Belzer, Clara; Stoof, Jeroen; Beckwith, Catherine S.; Kuipers, Ernst J.; Kusters, Johannes G.; Vliet, Arnoud H. M. van

doi:10.1099/mic.0.28188-0

Cited by 30 publications

(43 citation statements)

References 37 publications

(43 reference statements)

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“…The urease enzyme is an important virulence factor in gastric Helicobacter species such as Helicobacter pylori and Helicobacter mustelae (2,15,34), but a contribution of urease in the development of H. hepaticus-associated disorders is yet to be demonstrated. We have previously demonstrated that urease expression in H. hepaticus is neither nickel or pH responsive nor growth phase regulated (5). This contrasts with the situation in H. pylori, where urease expression is controlled by nickel and pH at the transcriptional, posttranscriptional, and translational levels (1,39,43,44).…”

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confidence: 39%

Iron-Responsive Repression of Urease Expression in Helicobacter hepaticus Is Mediated by the Transcriptional Regulator Fur

et al. 2007

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Persistent colonization of mucosal surfaces by bacteria in the mammalian host requires concerted expression of colonization factors, depending on the environmental conditions. Helicobacter hepaticus is a urease-positive pathogen that colonizes the intestinal and hepatobiliary tracts of rodents. Here it is reported that urease expression of H. hepaticus is iron repressed by the transcriptional regulator Fur. Iron restriction of growth medium resulted in a doubling of urease activity in wild-type H. hepaticus strain ATCC 51449 and was accompanied by increased levels of urease subunit proteins and ureA mRNA. Insertional inactivation of the fur gene abolished iron-responsive repression of urease activity, whereas inactivation of the perR gene did not affect iron-responsive regulation of urease activity. The iron-responsive promoter element was identified directly upstream of the H. hepaticus ureA gene. Recombinant H. hepaticus Fur protein bound to this ureA promoter region in a metal-dependent matter, and binding resulted in the protection of a 41-bp, Fur box-containing operator sequence located at positions ؊35 to ؊75 upstream of the transcription start site. In conclusion, H. hepaticus Fur controls urease expression at the transcriptional level in response to iron availability. This represents a novel type of urease regulation in ureolytic bacteria and extends the already diverse regulatory repertoire of the Fur protein.

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confidence: 39%

Iron-Responsive Repression of Urease Expression in Helicobacter hepaticus Is Mediated by the Transcriptional Regulator Fur

et al. 2007

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“…The ammonia produced from urea hydrolysis was measured by using the phenol/hypochlorite assay (Table 4). Addition of NiCl 2 to the medium dramatically increased the urease activity in the wild-type (from 0.06±0.02 units of specific activity in unsupplemented medium to 5.44±1.42 units in medium supplemented with 50 mM NiCl 2 ), as reported by Belzer et al (2005). Compared to the wild-type, urease activities were severely affected in all four mutants in non-nickel-supplemented medium, suggesting that hypA, hypB, ureE and ureG play a role in urease activity, as do their counterparts in H. pylori (Table 4).…”

Section: Hydrogenase and Urease Activity In Presence Of Various Amounmentioning

confidence: 53%

“…Analysis of the genome sequence of the mouse liver pathogen reveals the presence of a gene (hh0352) encoding a homologue of NikR, a nickel-responsive regulatory protein involved in urease regulation in H. pylori. However, Belzer et al (2005) have shown that the surge in urease activity in the wild-type was the consequence of a post-translational nickel activation of the apourease rather than a transcriptional mechanism. This result is in good agreement with the finding that the four nickel-related mutants have similar amounts of urease, as shown by immunoblotting against UreA or UreB.…”

Section: Although Protein Sequences Of H Hepaticus and H Pylorimentioning

confidence: 99%

Nickel enzyme maturation in Helicobacter hepaticus: roles of accessory proteins in hydrogenase and urease activities

2007

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Helicobacter hepaticus, a causative agent of chronic hepatitis and hepatocellular carcinoma in mice, possesses a hydrogenase and a urease, both of which are nickel-containing enzymes. Analysis of the genome sequence of H. hepaticus revealed a full set of accessory genes which are required for the nickel maturation of each enzyme in other micro-organisms. Erythromycinresistant mutants were constructed in four of these genes, hypA, hypB, ureE and ureG. Controls for polar effect were provided for hypA or hypB mutants by disrupting each gene located immediately downstream, i.e. hp0809 or hypC, respectively. Urease and hydrogenase activities were determined for each strain with or without supplemented nickel in the medium. As expected, the ureE and the ureG mutants had negligible urease activity, but they retained normal levels of hydrogenase activity. Urease levels could not be increased by the addition of nickel to the medium. The H. hepaticus hypA and hypB strains were deficient in both urease and hydrogenase activities, suggesting that both gene products act in a similar fashion as their counterparts in H. pylori. However, in contrast with the analogous mutants of H. pylori, the addition of nickel into the growth medium failed to restore either urease or hydrogenase enzyme levels in the H. hepaticus hypA or hypB mutants, indicating a probably unique role for these genes in the mouse liver pathogen.

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“…Therefore, urea metabolism and urease activity, in particular, have been implicated in the ability of certain bacteria to infect and cause disease (4,8,38). Examination of the urease gene cluster of the swine pathogen A. pleuropneumoniae (5) resulted in the identification and cloning of a putative urea transporter cDNA encoding a 300-amino acid protein ApUT (GenBank accession no.…”

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confidence: 99%

Functional characterization ofActinobacillus pleuropneumoniaeurea transport protein, ApUT

Godara¹,

Smith²,

Bossé³

et al. 2009

American Journal of Physiology-Regulatory, Integrative and Comp

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Urea transporters (UTs) effect rapid flux of urea across biological membranes. In the mammalian kidney, UT activity is essential for effective urine concentration. In bacteria, UT-mediated urea uptake permits intracellular urease to degrade urea to ammonia and CO2, a process that either buffers acid loads or provides nutrient nitrogen. We have characterized the urea transport channel protein ApUT from Actinobacillus pleuropneumoniae. Kinetic analysis of bacterial inside-out membranes enriched in ApUT showed ∼28-fold increase in urea permeability (3.3 ± 0.4 × 10−4cm/s) compared with control vesicles (0.11 ± 0.02 × 10−4cm/s). In addition to urea, ApUT also conducts water. Urea and water transport across the channel was phloretin and mercury inhibitable, and the site of inhibition may be located on the cytoplasmic side of the protein. Glycerol and urea analogs, such as methylamine, dimethylurea, formamide, acetamide, methylurea, propanamide, and ethylamine did not permeate across ApUT.

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Differential regulation of urease activity in Helicobacter hepaticus and Helicobacter pylori

Cited by 30 publications

References 37 publications

Iron-Responsive Repression of Urease Expression in Helicobacter hepaticus Is Mediated by the Transcriptional Regulator Fur

Iron-Responsive Repression of Urease Expression in Helicobacter hepaticus Is Mediated by the Transcriptional Regulator Fur

Nickel enzyme maturation in Helicobacter hepaticus: roles of accessory proteins in hydrogenase and urease activities

Functional characterization ofActinobacillus pleuropneumoniaeurea transport protein, ApUT

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