Regulation of the<i>nfsA</i>Gene in<i>Escherichia coli</i>by SoxS

Paterson, E. Suzanne; Boucher, Sherri E.; Lambert, Iain B.

doi:10.1128/jb.184.1.51-58.2002

Cited by 37 publications

(30 citation statements)

References 56 publications

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“…In addition, NADPH is the reductant or essential cofactor for several enzymes involved in protective and/or antioxidant activities, including glutathione reductase (GR), thioredoxin reductase, NADPH-dependent alkylhydroperoxidase and nitroreductase (Paterson et al, 2002;Imlay, 2008). Notably, several components of the soxRS and oxyR systems, such as glucose-6-phosphate dehydrogenase (G6PDH), ferredoxin-NADP(H) reductase (FPR), flavodoxin, GR and hydroperoxidase I are NADPHlinked enzymes or proteins.…”

Section: In Metabolic Terms Nadmentioning

confidence: 99%

The soxRS response of Escherichia coli can be induced in the absence of oxidative stress and oxygen by modulation of NADPH content

2011

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The soxRS regulon protects Escherichia coli cells against superoxide and nitric oxide. Oxidation of the SoxR sensor, a [2Fe-2S]-containing transcriptional regulator, triggers the response, but the nature of the cellular signal sensed by SoxR is still a matter of debate. In vivo, the sensor is maintained in a reduced, inactive state by the activities of SoxR reductases, which employ NADPH as an electron donor. The hypothesis that NADPH levels affect deployment of the soxRS response was tested by transforming E. coli cells with genes encoding enzymes and proteins that lead to either build-up or depletion of the cellular NADPH pool. Introduction of NADP + -reducing enzymes, such as wheat non-phosphorylating glyceraldehyde-3-phosphate dehydrogenase or E. coli malic enzyme, led to NADPH accumulation, inhibition of the soxRS regulon and enhanced sensitivity to the superoxide propagator methyl viologen (MV). Conversely, expression of pea ferredoxin (Fd), a redox shuttle that can oxidize NADPH via ferredoxin-NADP(H) reductase, resulted in execution of the soxRS response in the absence of oxidative stress, and in higher tolerance to MV. Processes that caused NADPH decline, including oxidative stress and Fd activity, correlated with an increase in total (NADP + +NADPH) stocks. SoxS expression can be induced by Fd expression or by MV in anaerobiosis, under conditions in which NADPH is oxidized but no superoxide can be formed. The results indicate that activation of the soxRS regulon in E. coli cells exposed to superoxide-propagating compounds can be triggered by depletion of the NADPH stock rather than accumulation of superoxide itself. They also suggest that bacteria need to finely regulate homeostasis of the NADP(H) pool to enable proper deployment of this defensive response.

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Section: In Metabolic Terms Nadmentioning

confidence: 99%

The soxRS response of Escherichia coli can be induced in the absence of oxidative stress and oxygen by modulation of NADPH content

2011

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“…The protein homologous to NfrA in E. coli, NfsA, shares 37% amino acids with the NfrA protein of S. aureus. This protein is transcribed in an operon in which ybjC, a small ORF whose function is unknown, is located upstream of nfsA (19,30). In contrast to B. subtilis and E. coli, we found that the nfrA gene is transcribed monocistronically in S. aureus.…”

Section: Discussionmentioning

confidence: 65%

Staphylococcus aureus NfrA (SA0367) Is a Flavin Mononucleotide-Dependent NADPH Oxidase Involved in Oxidative Stress Response

et al. 2005

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The NfrA protein, a putative essential oxidoreductase in the soil bacterium Bacillus subtilis, is induced under heat shock and oxidative stress conditions. In order to characterize the function of an homologous NfrA protein in Staphylococcus aureus, an nfrA deletion strain was constructed, the protein was purified, the enzymatic activity was determined, and the transcriptional regulation was investigated. The experiments revealed that NfrA is not essential in S. aureus. The purified protein oxidized NADPH but not NADH, producing NADP in the presence of flavin mononucleotide, suggesting that NfrA is an NADPH oxidase in S. aureus. In addition, the NfrA enzyme showed nitroreductase activity and weak disulfide reductase activity. Transcription was strongly induced by ethanol, diamide, and nitrofurantoin. Hydrogen peroxide induced nfrA transcription only at high concentrations. The expression of nfrA was independent of the alternative sigma factor B . Furthermore, the transcriptional start site was determined, which allowed identification of a PerR box homologous sequence upstream of the nfrA promoter. The observations presented here suggest that NfrA is a nonessential NADPH oxidoreductase which may play a role in the oxidative stress response of S. aureus, especially in keeping thiol-disulfide stress in balance.Staphylococcus aureus is a widely distributed opportunistic pathogen that is often part of the normal flora of the upper respiratory tract, as well as the skin surface, of healthy individuals. Under opportune circumstances, however, S. aureus can cause a wide variety of human diseases, which can range from mild superficial skin infections to deep and systemic infections, such as endocarditis, osteomyelitis, and septicemia (20). In addition, S. aureus is a common food pathogen that produces various superantigenic enterotoxins (6). As S. aureus is a typical nosocomial pathogen that causes up to 17% of all hospital-related infections and antibiotic treatment is essential to cure patients, the recent spread of antibiotic-resistant strains has raised major concerns worldwide (35). Most alarmingly, high-level vanA vancomycin resistance has recently been transferred from Enterococcus faecalis to S. aureus in the hospital setting (39). This event has spawned the fear that in the near future superbugs that are refractory to any antibiotic treatment will develop. Therefore, there is an urgent need to find new target structures for treatment, preferably components of pathways or cellular structures which are not targeted by currently used antibiotics (33).To conquer different environmental niches, bacteria must adapt quickly to the changing conditions by enhanced expression of a certain subset of genes. For example, during the oxidative stress caused by oxygen-derived radicals or the disulfide stress under thiol-oxidizing conditions, several oxidoreductive systems are activated (14,16,18,26,36). For Bacillus subtilis, DNA microarray analysis revealed that NfrA is induced by superoxide stress and H 2 O 2 stress. These re...

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“…The 6His-SoxS purified protein, kindly provided by Paratek Pharmaceuticals, Boston, MA, or purified as described previously (36), was produced by cloning the soxS gene into the pET-15b expression plasmid and subsequently purifying the His-tagged protein. DNA containing the fumC, gnd, or znuC promoters was amplified by PCR using the primer pairs fumCF1/fumCR1, gndF/gndR, and znuC-proF/znuC-proR; the products were gel purified.…”

Section: Methodsmentioning

confidence: 99%

SoxS Increases the Expression of the Zinc Uptake System ZnuACB in an Escherichia coli Murine Pyelonephritis Model

Warner¹,

Levy²

2011

Journal of Bacteriology

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Paralogous transcriptional regulators MarA, Rob, and SoxS act individually and together to control expression of more than 80 Escherichia coli genes. Deletion of marA, rob, and soxS from an E. coli clinical isolate prevents persistence beyond 2 days postinfection in a mouse model of pyelonephritis. We used microarray analysis to identify 242 genes differentially expressed between the triple deletion mutant and its parent strain at 2 days postinfection in the kidney. One of these, znuC of the zinc transport system ZnuACB, displayed decreased expression in the triple mutant compared to that in the parental strain, and deletion of znuC from the parental strain reduced persistence. The marA rob soxS triple deletion mutant was less viable in vitro under limited-Zn and Zn-depleted conditions, while disruption of znuC caused a reduction in the growth rates for the parental and triple mutant strains to equally low levels under limited-Zn or Zn-depleted conditions. Complementation of the triple mutant with soxS, but not marA or rob, restored the parental growth rate in Zn-depleted medium, while deletion of only soxS from the parental strain led to low growth in Zn-depleted medium. Both results suggested that SoxS is a major regulator responsible for growth under Zn-depleted conditions. Gel shift experiments failed to show direct binding of SoxS to the znuCB promoter, thus suggesting indirect control of znuCB expression by SoxS. While SoxS expression in the triple mutant fully restored persistence, increased expression of znuACB via a plasmid in this mutant only partially restored wild-type levels of persistence in the kidney. This work implicates SoxS control of znuCB expression as a key factor in persistence of E. coli in murine pyelonephritis.

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Regulation of thenfsAGene inEscherichia coliby SoxS

Cited by 37 publications

References 56 publications

The soxRS response of Escherichia coli can be induced in the absence of oxidative stress and oxygen by modulation of NADPH content

The soxRS response of Escherichia coli can be induced in the absence of oxidative stress and oxygen by modulation of NADPH content

Staphylococcus aureus NfrA (SA0367) Is a Flavin Mononucleotide-Dependent NADPH Oxidase Involved in Oxidative Stress Response

SoxS Increases the Expression of the Zinc Uptake System ZnuACB in an Escherichia coli Murine Pyelonephritis Model

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