Role of Hpn and NixA of <i>Helicobacter pylori</i> in Susceptibility and Resistance to Bismuth and Other Metal Ions

Mobley, Harry L. T.; Garner, Rachel M.; Chippendale, G. R.; Gilbert, Joanne V.; Kane, Anne; Plaut, Andrew G.

doi:10.1046/j.1523-5378.1999.99286.x

Cited by 60 publications

(65 citation statements)

References 23 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Hpn is also present in the ferret and cat gastric Helicobacter pathogens, but it is absent from the mouse (liver) pathogen H. hepaticus. H. pylori mutants lacking hpn were more sensitive to nickel and bismuth than the parent strain, but a nixA strain was not more sensitive; this indicates that Hpn may sequester metals that accumulate internally via a passive equilibrium mechanism (from a high external metals environment) (Mobley et al 1999). As nixA itself is regulated by nickel levels (through NikR) , it would seem to be of benefit to H. pylori to have Hpn proteins available to detoxify rapid fluxes in metal levels.…”

Section: Hpn and Hpn-like Proteinsmentioning

confidence: 98%

“…To further explore the roles of these (hpn and hpn-like) genes, individual gene-disruption mutant strains were created, and a double mutant lacking genes for both these histidine rich proteins was also studied (Seshadri, Benoit, Maier, unpublished data, ASM Abstract 2005). Previous results showed that an hpn mutant is more sensitive to nickel than is wild-type (Mobley et al 1999). Recent preliminary studies (S. Seshadri and R. Maier, abstract D21, 105th general meeting ASM, 2005) indicate the Hpn-like protein also may play a role in nickel detoxification.…”

Section: Hpn and Hpn-like Proteinsmentioning

confidence: 99%

See 1 more Smart Citation

Nickel-binding and accessory proteins facilitating Ni-enzyme maturation in Helicobacter pylori

2007

View full text Add to dashboard Cite

Helicobacter pylori colonizes the human gastric mucosa and this can lead to chronic gastritis, peptic and duodenal ulcers, and even gastric cancers. The bacterium colonizes over one-half of the worlds population. Nickel plays a major role in the bacteriums colonization and persistence attributes as two nickel enzyme sinks obligately contain the metal. Urease accounts for up to 10% of the total cellular protein made and is required for initial colonization processes, and the hydrogen oxidizing hydrogenase provides the bacterium a high-energy substrate yielding low potential electrons for energy generation. A battery of accessory proteins are needed for maturation or activation of each of the apoen-zymes. These include Ni-chaperones and GTPas-es, some of which are unique to each Ni-enzyme and others that are individually required for maturation of both the Ni-enzymes. H. pylori's need for some conventional hydrogenase maturation proteins playing roles in urease maturation may have to do with the poor nickel-sequestering ability of the UreE urease maturation protein compared to other systems. H. pylori also possesses a NixA nickel specific permease, a nickel dependent regulator (NikR), a recently identified nickel efflux system (CznABC), and a histidinerich heat shock protein, HspA. Based on mutant analysis approaches all these proteins have roles in nickel homeostasis, in urease expression, and in host colonization. The His-rich putative nickel storage proteins Hpn and Hpn-like play roles in nickel detoxification and may influence the levels of Ni-activated urease that can be achieved.

show abstract

Section: Hpn and Hpn-like Proteinsmentioning

confidence: 98%

Section: Hpn and Hpn-like Proteinsmentioning

confidence: 99%

Nickel-binding and accessory proteins facilitating Ni-enzyme maturation in Helicobacter pylori

2007

View full text Add to dashboard Cite

show abstract

“…De novo synthesis of NikR was not required for the mutant phenotypes, because inhibition of translation by chloramphenicol or erythromycin had no effect (data not shown). Single or double mutant strains with deletions of genes involved in Ni 2ϩ transport (nixA [28] and exbBD tonB [36]), Ni 2ϩ storage (hpn and hpn-like [6,19,29,37]), and Ni 2ϩ efflux (cznABC [39]) also showed no changes in NikR-dependent regulation (data not shown). This contrasts with results from E. coli, where the Ni 2ϩ efflux protein RcnA impedes NikR activation under nickel-limiting conditions (23).…”

mentioning

confidence: 98%

An Intact Urease Assembly Pathway Is Required To Compete with NikR for Nickel Ions in Helicobacter pylori

Benanti

Chivers

2009

J Bacteriol

View full text Add to dashboard Cite

We examined the effects of urease and hydrogenase assembly gene deletions on NikR activation in H. pylori strains 26695 and G27. The loss of any component of urease assembly increased NikR activity under Ni 2؉ -limiting conditions, as measured by reduced transcript levels and 63 Ni accumulation. Additionally, SlyD functioned in urease assembly in strain 26695.A diverse complement of proteins is dedicated to the acquisition, trafficking, and regulation of intracellular transition metal ions. The mechanisms by which these activities are integrated to allocate the appropriate proportion of metal to different metal-binding proteins are not yet understood. Additionally, studies of the equilibrium metal-binding properties of transcriptional regulatory proteins important for metal homeostasis have revealed that they avidly bind their cognate metal ions (10 8,9,22,33,42]). These observations suggest that competition may exist between metalloenzyme assembly and metalloregulation. Detailed investigations of this hypothesis are encumbered by the presence of numerous essential metalloenzymes for metals such as zinc and iron. Microbial nickel physiology provides an ideal system for studying intracellular metal competition due to the small number of enzymes that require nickel ions (30) and their nonessentiality under laboratory growth conditions.We have studied the effect of disrupting Ni 2ϩ -dependent enzyme assembly pathways on nickel-dependent gene regulation in the gram-negative gastric pathogen Helicobacter pylori (3). The two Ni 2ϩ -dependent enzymes of H. pylori, urease and hydrogenase, are required for efficient colonization of animal models of infection (15,16,31). Both enzymes require conserved, GTP-dependent pathways for metal cofactor assembly that include an absolute requirement for nickel insertion chaperones under metal-limiting conditions (30). Hausinger and coworkers identified UreE as the Ni 2ϩ -binding protein required for urease assembly in Klebsiella aerogenes (10,38 before NikR, and the subsequent repression of nickel uptake genes. Such competition, if present, would be manifested as a change in NikR activity independently of a change in total nickel levels. In the absence of competition, NikR activity would correlate with a fixed total nickel concentration, independent of Ni 2ϩ -dependent enzyme expression or biosynthesis. Competition between metalloenzymes and metalloregulatory proteins has not been tested. Demonstration of the nature of such competition would facilitate subsequent studies to understand the molecular basis of metal ion partitioning within cells.We examined the effects of Ni 2ϩ -dependent enzyme assembly pathway gene deletions on NikR activity using several assays. In each case, cells were grown under identical conditions and manipulated in the same way for the same length of time. Cells were grown for 20 h (26695) or 24 h (G27) to an optical density at 600 nm of 1.0 in brucella broth (BD Difco) with 5% fetal bovine serum (Sigma) and then exposed to either 100 M dimethylglyoxime (DMG),...

show abstract

“…Besides nickel, CorA can also transport cobalt and maybe ferrous iron (39). It has been shown that H. pylori is especially sensitive to cobalt (38), a metal which is not transported via NixA (T. Eitinger, personal communication).…”

mentioning

confidence: 99%

“…The uptake, toxicity, resistance, and regulatory capacities of transition metals, especially the roles of iron (4,5,52) and nickel (38,51), have been the subjects of several investigations of H. pylori. Since the role of nickel is ambivalent (it is toxic at higher concentrations but it is essential for urease activity), a delicate equilibrium of nickel uptake, storage, and incorporation into target enzymes is therefore necessary.…”

mentioning

confidence: 99%

Nickel Represses the Synthesis of the Nickel Permease NixA ofHelicobacter pylori

Wolfram¹,

Haas

Bauerfeind³

2006

J Bacteriol

View full text Add to dashboard Cite

Nickel acquisition is necessary for urease activity, a major virulence factor of the human gastric pathogen Helicobacter pylori. NixA was identified as a specific nickel uptake system in this organism. Addition of small amounts of nickel to media strongly stimulates urea hydrolysis. On the other hand, high nickel concentrations are deleterious to cell growth. As a possible protective reaction, nickel uptake seems to be reduced in H. pylori grown in nickel-rich media. These observations led to investigations of regulation of the expression of the nickel permease NixA. We found that increasing the nickel concentration in media reduced the amount of NixA. In order to address the question of whether this phenomenon was subject to transcriptional or translational regulation, we quantified nixA mRNA from H. pylori by real-time PCR. The amount of nixA mRNA was gradually reduced five-to sevenfold in a time-and concentration-dependent manner. Repression could be measured as soon as 5 min after nickel addition, and the maximum repression occurred after 20 to 30 min. The maximum repression was obtained with an external nickel concentration of 100 M. The observed nickel repression of NixA was dependent on nikR encoding the nickel-responsive regulatory protein NikR. In conclusion, we demonstrated that synthesis of the NixA nickel permease of H. pylori shows nickel-responsive regulation mediated by NikR to maintain the balance between effective nickel acquisition and a toxic overload.

show abstract

Role of Hpn and NixA of Helicobacter pylori in Susceptibility and Resistance to Bismuth and Other Metal Ions

Abstract: We concluded that bacteria lacking Hpn, cultured in vitro, are more susceptible than is the wild type to bismuth and Ni2+.

Cited by 60 publications

References 23 publications

Nickel-binding and accessory proteins facilitating Ni-enzyme maturation in Helicobacter pylori

Nickel-binding and accessory proteins facilitating Ni-enzyme maturation in Helicobacter pylori

An Intact Urease Assembly Pathway Is Required To Compete with NikR for Nickel Ions in Helicobacter pylori

Nickel Represses the Synthesis of the Nickel Permease NixA ofHelicobacter pylori

Contact Info

Product

Resources

About