Nickel Represses the Synthesis of the Nickel Permease NixA of<i>Helicobacter pylori</i>

Wolfram, Lutz; Haas, Elvira; Bauerfeind, Peter

doi:10.1128/jb.188.4.1245-1250.2006

Cited by 50 publications

(64 citation statements)

References 55 publications

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“…Deletion of nikR in each mutant background restored 63 Ni accumulation to levels similar to those of a nikR mutant strain (ϳ120 to 150% of the level in the parental strain). These data provide further evidence that NikR activity is increased in the urease pathway mutants and indicate that the decrease in nixA and frpB4 levels results in decreased NixA and FrpB4 protein levels during this assay, consistent with a previous report of the rate of NixA turnover under similar conditions (44).…”

supporting

confidence: 79%

“…1a to d), respectively, in a NikR-dependent manner (14,17,18,44). nixA and frpB4 levels in the nikR mutant strain treated with DMG or NiCl 2 were also increased relative to levels in the parent strain ( Fig.…”

mentioning

confidence: 89%

“…Genetic and biochemical studies have shown direct NikR-dependent regulation of genes required for nickel import (nixA [5,17,44], fecA3 [18], frpB4 [14,18], and exbBD tonB [18]), Ni 2ϩ -dependent enzyme activity (ureAB [1,5,17]), and nickel storage (hpn [11]). Because NikR represses all currently known nickel import genes (nixA, fecA3, frpB4, and exbBD tonB) (14,17,18,44), Ni 2ϩ -dependent enzyme biosynthesis pathways must acquire Ni 2ϩ 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.…”

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confidence: 99%

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

Benanti

Chivers

2009

J Bacteriol

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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),...

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confidence: 79%

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confidence: 89%

mentioning

confidence: 99%

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

Benanti

Chivers

2009

J Bacteriol

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“…For instance, while we have shown that the Hpn and Hpn-like proteins play a role in nickel (and other metal) detoxification, the role of these proteins in concert with other metal toxicity prevention mechanisms is not understood. High nickel levels repress expression of the NixA transporter and the other Niresponsive outer membrane protein studied (7,9,39), presumably to aid in preventing nickel toxicity; perhaps the His-rich proteins provide a more rapid (detoxification) response to transient nickel fluctuations before the (transporter) expression changes can have an affect. Also, Ni efflux pumps (CznABC) that are proposed to pump out excess nickel have been identified (28); this adds another feature to the overall Ni homeostasis/detoxification picture.…”

Section: Discussionmentioning

confidence: 99%

Roles of His-Rich Hpn and Hpn-Like Proteins in Helicobacter pylori Nickel Physiology

2007

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Individual gene-targeted hpn and hpn-like mutants and a mutant with mutations in both hpn genes were more sensitive to nickel, cobalt, and cadmium toxicity than was the parent strain, with the hpn-like strain showing the most metal sensitivity of the two individual His-rich protein mutants. The mutant strains contained up to eightfold more urease activity than the parent under nickel-deficient conditions, and the parent strain was able to achieve mutant strain activity levels by nickel supplementation. The mutants contained 3-to 4-fold more and the double mutant about 10-fold more Ni associated with their total urease pools, even though all of the strains expressed similar levels of total urease protein. Hydrogenase activities in the mutants were like those in the parent strain; thus, hydrogenase is fully activated under nickel-deficient conditions. The histidine-rich proteins appear to compete with the Ni-dependent urease maturation machinery under lownickel conditions. Upon lowering the pH of the growth medium from 7.3 to 5, the wild-type urease activity increased threefold, but the activity in the three mutant strains was relatively unaffected. This pH effect was attributed to a nickel storage role for the His-rich proteins. Under low-nickel conditions, the addition of a nickel chelator did not significantly affect the urease activity of the wild type but decreased the activity of all of the mutants, supporting a role for the His-rich proteins as Ni reservoirs. These nickel reservoirs significantly impact the active urease activities achieved. The His-rich proteins play dual roles, as Ni storage and as metal detoxification proteins, depending on the exogenous nickel levels.

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“…Secondly, the nik-specific repressor NikR allows expression of the nik operon only at low environmental nickel levels (de Pina et al, 1995). In H. pylori, NikR is crucial to controlling both nickel transport (Ernst et al, 2005;Wolfram et al, 2006) and urease expression (van Vliet et al, 2002). The H. pylori NikR is a highly pleiotropic regulator that is able to act as a repressor or activator (Ernst et al, 2005) of a large number of genes (Contreras et al, 2003), as well as responding to low pH (Bury-Moné et al, 2004;van Vliet et al, 2004).…”

Section: Discussionmentioning

confidence: 99%

Hydrogenase activity in the foodborne pathogen Campylobacter jejuni depends upon a novel ABC-type nickel transporter (NikZYXWV) and is SlyD-independent

et al. 2012

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Campylobacter jejuni is a human pathogen of worldwide significance. It is commensal in the gut of many birds and mammals, where hydrogen is a readily available electron donor. The bacterium possesses a single membrane-bound, periplasmic-facing NiFe uptake hydrogenase that depends on the acquisition of environmental nickel for activity. The periplasmic binding protein Cj1584 (NikZ) of the ATP binding cassette (ABC) transporter encoded by the cj1584c-cj1580c (nikZYXWV) operon in C. jejuni strain NCTC 11168 was found to be nickel-repressed and to bind free nickel ions with a submicromolar K d value, as measured by fluorescence spectroscopy. Unlike the Escherichia coli NikA protein, NikZ did not bind EDTA-chelated nickel and lacks key conserved residues implicated in metallophore interaction. A C. jejuni cj1584c null mutant strain showed an approximately 22-fold decrease in intracellular nickel content compared with the wildtype strain and a decreased rate of uptake of 63 NiCl 2 . The inhibition of residual nickel uptake at higher nickel concentrations in this mutant by hexa-ammine cobalt (III) chloride or magnesium ions suggests that low-affinity uptake occurs partly through the CorA magnesium transporter. Hydrogenase activity was completely abolished in the cj1584c mutant after growth in unsupplemented media, but was fully restored after growth with 0.5 mM nickel chloride. Mutation of the putative metallochaperone gene slyD (cj0115) had no effect on either intracellular nickel accumulation or hydrogenase activity. Our data reveal a strict dependence of hydrogenase activity in C. jejuni on high-affinity nickel uptake through an ABC transporter that has distinct properties compared with the E. coli Nik system.

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Nickel Represses the Synthesis of the Nickel Permease NixA ofHelicobacter pylori

Cited by 50 publications

References 55 publications

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

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

Roles of His-Rich Hpn and Hpn-Like Proteins in Helicobacter pylori Nickel Physiology

Hydrogenase activity in the foodborne pathogen Campylobacter jejuni depends upon a novel ABC-type nickel transporter (NikZYXWV) and is SlyD-independent

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