Mechanism of chromate reduction by the <i>Escherichia coli</i> protein, NfsA, and the role of different chromate reductases in minimizing oxidative stress during chromate reduction

Ackerley, David F.; González, Claudio F.; Keyhan, M.; Blake, Robert C.; Матин, А.

doi:10.1111/j.1462-2920.2004.00639.x

Cited by 236 publications

(147 citation statements)

References 27 publications

(57 reference statements)

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“…Despite this, the chrR mutant was impaired relative to wild type, not only in chromate transformation rate but also in viability in the presence of chromate (3). We speculated, then, that the protective effect of ChrR might stem from an ability to pre-empt one-electron reducers from carrying out a partial reduction of Cr(VI) to the redox-cycling species Cr(V) and subsequently provided in vitro experimental evidence supporting this hypothesis (4). However, in light of the data presented here, it now seems likely that the quinonemediated antioxidant activity of ChrR was also a significant factor contributing to the superior viability of the wild type cells.…”

Section: Fig 2 H 2 O 2 -Scavenging (Open Symbols) and Growth (As Mementioning

confidence: 99%

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ChrR, a Soluble Quinone Reductase of Pseudomonas putida That Defends against H2O2

González¹,

Ackerley²,

Lynch

et al. 2005

Journal of Biological Chemistry

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Most bacteria contain soluble quinone-reducing flavoenzymes. However, no biological benefit for this activity has previously been demonstrated. ChrR of Pseudomonas putida is one such enzyme that has also been characterized as a chromate reductase; yet we propose that it is the quinone-reducing activity of ChrR that has the greatest biological significance. ChrR reduces quinones by simultaneous two-electron transfer, avoiding formation of highly reactive semiquinone intermediates and producing quinols that promote tolerance of H 2 O 2 . Expression of chrR was induced by H 2 O 2 , and levels of chrR expression in overexpressing, wild type, and knock-out mutant strains correlated with the H 2 O 2 tolerance and scavenging ability of each strain. The chrR expression level also correlated with intracellular H 2 O 2 levels as measured by protein carbonylation assays and fluorescence-activated cell scanning analysis with the H 2 O 2 -responsive dye H 2 DCFDA. Thus, enhancing the activity of ChrR in a chromate-remediating bacterial strain may not only increase the rate of chromate transformation, it may also augment the capacity of these cells to withstand the unavoidable production of H 2 O 2 that accompanies chromate reduction.

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Section: Fig 2 H 2 O 2 -Scavenging (Open Symbols) and Growth (As Mementioning

confidence: 99%

“…However, high cell densities are generally required for significant levels of Cr(VI) transformation, and an effective system for in situ bioremediation has yet to be developed. To enhance this activity, we have proposed molecular engineering of cells and enzymes to decrease chromate toxicity to bacteria and increase chromate transformation (3)(4)(5).…”

mentioning

confidence: 99%

ChrR, a Soluble Quinone Reductase of Pseudomonas putida That Defends against H2O2

González¹,

Ackerley²,

Lynch

et al. 2005

Journal of Biological Chemistry

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132

119

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“…The concentration of hexavalent chromium, Cr(VI), in the culture media was determined spectrophotometrically using 1, 5-diphenylcarbazide as complexing agent [24,[28][29][30]. One milliliter (1 ml) of 0.2 % w/v of 1, 5-diphenylcarbazide solution (prepared in 95% ethanol and 1 ml of 1 / 5 H 2 SO 4 ) was added to 1 ml of the sample solution.…”

Section: Determination Of Cr(vi) Cr(iii) and Cr T Concentrations In mentioning

confidence: 99%

Uptake and Reduction of Hexavalent Chromium by Aspergillus Niger and Aspergillus Parasiticus

Shugaba¹,

Buba²,

Bg³

et al. 2012

J Pet Environ Biotechnol

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The uptake and reduction of Cr(VI) by Aspergillus niger and A. parasiticus was studied in this journal. After 96 hours of growth, the culture solutions spiked with an initial dichromate concentration of 20 mg/l, were completely decolorized and had residual Cr(VI) concentrations of only 0.74 ± 0.55 and 1.69 ± 0.29 mg/l in A. niger and A. parasiticus cultures representing Cr(VI) removal of 96.3% and 91.6%, respectively. In the A. niger culture, significantly (P < 0.01) lower Cr(VI) concentrations were observed within 72 hours of growth compared to those of A. parasiticus, but in both cultures complete removal was almost achieved by 144 hours of growth. The rate of Cr(VI) removal was 0.21 ± 0.09 mgl -1 hr -1 and 0.20 ± 0.07 mgl -1 hr -1 for A. niger and A. parasiticus, respectively. Cellular concentrations of Cr(VI) in the two fungi increased significantly (P < 0.05 -0.001) with increasing concentrations of the dichromate treatments. Although tannic acid as sole source of carbon and energy gave significantly lower Cr(VI) removal than glucose (P < 0.001) and acetate (P < 0.01), it supported the removal of about 85.0% and 68.8% of the metal ion by A. niger and A. parasiticus, respectively. The active mycelia of both fungi showed significantly (P < 0.001) higher Cr(VI) removal than inactivated mycelia after incubation at 30°C for 72 hours. Incubation of cell -free extracts of both fungi with NADH at 30°C for 2 hours showed Cr(VI) reduction of 68.0% and 55.5% for A. niger and A. parasiticus, respectively. These findings suggest that uptake and metabolic reduction may be the process by which the two fungi are able to tolerate the toxic effects of hexavalent chromium. However, Cr removal via uptake by the two fungal biomass was observed to be in the range of 0.5 -1.78% only, for all the concentrations applied, which is insignificant when compared with the initial Cr concentration in the culture medium. The results obtained through this investigation indicate the possibility of treating waste effluents containing hexavalent chromium using Aspergillus niger and A. parasiticus.

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“…Cr(VI) accumulated by organisms is reduced to Cr(III) with the concomitant production of intermediate Cr (V) and Cr(IV) products and oxygen-and carbon-based radicals (Cervantes et al, 2001;O'Brien et al, 2001;Ackerley et al, 2004). These species are known to be associated with a spectrum of DNA lesions occurring during Cr(VI) exposure (Aiyar et al, 1991;Luo et al, 1996;O'Brien et al, 2002;Reynolds et al, 2004), many of which are oxidative in nature.…”

Section: Introductionmentioning

confidence: 99%

Oxidative protein damage causes chromium toxicity in yeast

et al. 2005

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Oxidative damage in microbial cells occurs during exposure to the toxic metal chromium, but it is not certain whether such oxidation accounts for the toxicity of Cr. Here, a Saccharomyces cerevisiae sod1D mutant (defective for the Cu,Zn-superoxide dismutase) was found to be hypersensitive to Cr(VI) toxicity under aerobic conditions, but this phenotype was suppressed under anaerobic conditions. Studies with cells expressing a Sod1p variant (Sod1 H46C ) showed that the superoxide dismutase activity rather than the metal-binding function of Sod1p was required for Cr resistance. To help identify the macromolecular target(s) of Cr-dependent oxidative damage, cells deficient for the reduction of phospholipid hydroperoxides (gpx3D and gpx1D/gpx2D/gpx3D) and for the repair of DNA oxidation (ogg1D and rad30D/ogg1D) were tested, but were found not to be Cr-sensitive. In contrast, S. cerevisiae msraD (mxr1D) and msrbD (ycl033cD) mutants defective for peptide methionine sulfoxide reductase (MSR) activity exhibited a Cr sensitivity phenotype, and cells overexpressing these enzymes were Cr-resistant. Overexpression of MSRs also suppressed the Cr sensitivity of sod1D cells. The inference that protein oxidation is a primary mechanism of Cr toxicity was corroborated by an observed~20-fold increase in the cellular levels of protein carbonyls within 30 min of Cr exposure. Carbonylation was not distributed evenly among the expressed proteins of the cells; certain glycolytic enzymes and heat-shock proteins were specifically targeted by Cr-dependent oxidative damage. This study establishes an oxidative mode of Cr toxicity in S. cerevisiae, which primarily involves oxidative damage to cellular proteins.

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Mechanism of chromate reduction by the Escherichia coli protein, NfsA, and the role of different chromate reductases in minimizing oxidative stress during chromate reduction

Cited by 236 publications

References 27 publications

ChrR, a Soluble Quinone Reductase of Pseudomonas putida That Defends against H2O2

ChrR, a Soluble Quinone Reductase of Pseudomonas putida That Defends against H2O2

Uptake and Reduction of Hexavalent Chromium by Aspergillus Niger and Aspergillus Parasiticus

Oxidative protein damage causes chromium toxicity in yeast

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