Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Nitroreductases”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 55 records · Page 3Linked to original sources
PubMed2004

Virus-directed enzyme prodrug therapy: intratumoral administration of a replication-deficient adenovirus encoding nitroreductase to patients with resectable liver cancer.

PURPOSE: Virus-directed enzyme prodrug therapy depends on selective delivery of virus encoding a prodrug-activating enzyme to tumor, followed by systemic treatment with prodrug to achieve high levels of the activated cytotoxic at the intended site of action. The use of the bacterial enzyme nitroreductase to activate CB1954 (5-(aziridin-1-yl)-2,4-dinitrobenzamide) to a short lived, highly toxic DNA cross-linking agent has been demonstrated in tumor xenografts. In this study, we report the first clinical trial investigating the feasibility, safety, and transgene expression of a replication-defective adenovirus encoding nitroreductase (CTL102) in patients with liver tumors. PATIENTS AND METHODS: Patients with resectable primary or secondary (colorectal) liver cancer received a single dose of CTL102 delivered by direct intratumoral inoculation 3 to 8 days before surgical resection. RESULTS: Eighteen patients were treated with escalating doses of CTL102 (range, 10(8)-5 x 10(11) virus particles). The vector was well tolerated with minimal side effects, had a short half-life in the circulation, and stimulated a robust antibody response. Dose-related increases in tumoral nitroreductase expression measured by immunohistochemical analysis have been observed. CONCLUSION: Direct intratumoral inoculation of CTL102 to patients with primary and secondary liver cancer is feasible and well tolerated. The high level of nitroreductase expression observed at 1 to 5 x 10(11) virus particles mandates further studies in patients with inoperable tumors who will receive CTL102 and CB1954.

Adenoviridae↗
PubMed1993

Conversion of 4-nitroquinoline 1-oxide (4NQO) to 4-hydroxyaminoquinoline 1-oxide by a dicumarol-resistant hepatic 4NQO nitroreductase in rats and mice.

The product formed from 4-nitroquinoline 1-oxide (4NQO), a potent carcinogen, by the action of mouse NADH:4NQO nitroreductase NR-1 was directly identified as 4-hydroxyaminoquinoline 1-oxide (4HAQO) by high performance liquid chromatography analyses in two systems. In liver cytosols from both male and female mice, NADH:4NQO nitroreductase was the predominant enzyme catalyzing the reduction of 4NQO. Rat liver cytosol catalyzed the conversion of 4NQO to either 4HAQO or a glutathione conjugate depending upon coenzyme or cosubstrate availability. Whereas NAD(P)H:quinone reductase (NAD(P)H:(quinone acceptor) oxidoreductase; DT diaphorase; EC 1.6.99.2) was the predominant 4NQO reductase present in liver cytosol from Sprague-Dawley rats, dicumarol-resistant NADH:4NQO nitroreductase specific activities were comparable with those of mouse liver cytosols. A 4NQO nitroreductase from rat liver cytosol was separated from NAD(P)H:quinone reductase chromatographically and shown to have a strong preference for NADH and to be insensitive to inhibition by dicumarol.

4-Hydroxyaminoquinoline-1-oxide↗
PubMed2001

Potential involvement of several nitroreductases in metronidazole resistance in Helicobacter pylori.

Susceptibility of Helicobacter pylori to the antibiotic metronidazole has been attributed to the activity of an oxygen-insensitive NADPH-dependent nitroreductase (RdxA), with resistance to this antimicrobial arising from null mutations in rdxA. To obtain a better understanding of the factors involved in resistance, nitroreductase and metronidazole reduction activities were investigated in matched pairs of clinical and laboratory-derived sensitive and resistant H. pylori strains. Significant differences in enzyme activities were observed between sensitive and resistant strains, suggesting that metronidazole susceptibility in H. pylori was associated with more than one enzyme activity. To establish the mutations occurring in rdxA, the genes from seventeen bacterial strains, including matched pairs were sequenced. To assess whether metronidazole was responsible for inducing random mutations in this gene, the complete nucleotide sequence of gene hp0630, encoding an NAD(P)H-quinone reductase which also has NADPH-dependent nitroreductase activity, was determined in the same strains. All resistant strains showed nonsense, missense, or frameshift mutations randomly throughout rdxA. In contrast, no mutations were observed in hp0630. The results confirmed the presence of rdxA null mutations in resistant strains and suggested that other factors involved in the metabolism of metronidazole contributed to the resistant phenotype.

Amino Acid Sequence↗
PubMed1996

Mutagenicity of nitrophenanthrene derivatives for Salmonella typhimurium: effects of nitroreductase and acetyltransferase.

To determine the mutagenicity of nitrophenanthrenes, three mononitrophenanthrenes (NPhs), 11 dinitrophenanthrenes (diNPhs) and eight trinitrophenanthrenes (tiNPhs) were synthesized, and their mutagenicity was investigated by using Salmonella typhimurium his- strains TA98, TA100, and TA98NR, nitroreductase-deficient, and TA98/1,8-DNP6, O-acetyltransferase-deficient mutants, and strains YG1021 and YG1026, nitroreductase-overproducing mutants of TA98 and TA100, respectively, and strains YG1024 and YG1029, O-acetyltransferase-overproducing mutants of TA98 and TA100, respectively. 1-, 3- and 9-NPhis induced 329, 620 and 438 revertants per nmol in strain TA100, respectively, and 4,839, 11,309 and 16728 revertants per nmol, respectively, in strain YG1029. Mutagenicity of 1,6-, 2,6-, 2,9-, 2,10-, 3,5-, 3,6- and 3,10-diNPh was elevated in strains YG1021, YG1024, YG1026 and YG1029. Among these derivatives, 1,6-, 2,6-, 3,6- and 3,10-diNPhs were more mutagenic in strains YG1024 and YG1029 than YG1021 and YG1026, and they showed a structure-activity relationship between mutagenicity and NO2-substitution. Nitro derivatives substituted at the 3 and 6 positions of their chemical structure strongly mutated both strains YG1024 and YG1029, whereas those substituted at the 9 and 10 positions showed weak mutagenicity. In addition, nitro substituents at positions 4 and 5 were perpendicular while those on positions 2,3,6 and 7 were nearly coplanar to the aromatic ring. Furthermore, 2,6,9-, 3,6,9- and 1,6,9-trinitrophenanthrenes (triNPhs) were mutagenic for strain TA100, and their mutagenicity was more enhanced in YG1024 and YG1029 than in YG1021 and YG1026. Of the eight triNPhs all except 1,5,10-triNP were mutagenic in TA98 and TA100, and their mutagenicity was more enhanced in YG1024 and YG1029 than in YG1021 and YG1026. These results suggest that these compounds are mutagens that are activated by O-acetyltransferase esterification following nitroreductase. The nitrated derivatives substituted at the 2(7) and 3(6) positions of the phenanthrene ring were highly mutagenic. The relationship between chemical structure and the mutagenicity of NPh derivatives is discussed.

Acetyltransferases↗
PubMed1999

Influence of nitroreductase and O-acetyltransferase on the mutagenicity of substituted nitrobenzothiophenamines in Salmonella typhimurium.

The mutagenic activity of 17 substituted (aryl)(2-nitrobenzo[b]thiophen-3yl)amines has been evaluated in the Ames test with different isogenic strains of Salmonella typhimurium, that varied in their expression of nitroreductase and O-acetyltransferase. Active derivatives induced frameshift mutations in TA98 strain, and differences in the chemical structure resulted in up to 15-fold changes in mutagenic activity. The non-mutagenic compounds are the unsubstituted parent compound and derivatives with para-chloro, para-fluoro, para-diethylamino, meta-bromo and para-dimethylamino groups. They do not show any activity even in strains with higher level of nitroreductase or O-acetyltransferase. The addition of S9 fraction decreases the mutagenic potential or gives comparable results to those obtained without metabolic activation. For electron-donating substituents, the meta-isomers display the greatest mutagenic potency, whereas the transfer of the group to the para-position leads to less active or unactive molecules. All active nitrobenzothiophenes are substrates for bacterial nitroreductase and O-acetyltransferase, as shown by the reduced mutagenicity in the deficient strains and increased mutagenicity in the corresponding overproducing bacteria. Previous reports have pointed out interest in nitrothiophene analogues with para-chloro and para-fluoro substituents as promising anti-inflammatory drugs. The present study further enhances the putative interest in these derivatives, based on absence of mutagenicity.

Acetyltransferases↗
PubMed2003

Mechanism of metronidazole-resistance by isolates of nitroreductase-producing Enterococcus gallinarum and Enterococcus casseliflavus from the human intestinal tract.

Enterococcus casseliflavus and Enterococcus gallinarum strains resistant to metronidazole, nitrofurantoin and nitrofurazone were isolated from fecal samples of a patient with recurrent ulcerative colitis treated with metronidazole. Unlike other metronidazole-resistant bacteria, these strains produced nitroreductase but metabolized metronidazole to compounds that could not be detected by liquid chromatography with UV or mass spectral analysis. Metronidazole-susceptible Clostridium perfringens grew equally well in spent cultures of Enterococcus spp. incubated with or without metronidazole. These data indicate that the nitroreductases produced by these Enterococcus strains did not activate metronidazole to bactericidal metabolites and these bacteria may reduce the effectiveness of metronidazole. We have indirect evidence for an alternative pathway that results in metronidazole resistance. These strains of enterococcus had nitroreductase so resistance should not have occurred.

Chromatography, High Pressure Liquid↗
PubMed2000

Oxygen-insensitive nitroreductases of Escherichia coli do not reduce 3-nitrotyrosine.

The oxygen-insensitive nitroreductases nfsA and nfsB are known to reduce para-nitrated aromatic compounds. We tested the hypothesis that these nitroreductases are capable of reducing 3-nitrotyrosine in proteins and peptides, as well as in free amino acids using wild-type and nfsA nfsB mutant strains of Escherichia coli. E. coli homogenates were incubated with nitrated proteins and the level of 3-nitrotyrosine immunoreactivity was assayed by Western blotting. Assay conditions that allow the nitroreductases to rapidly reduce nitrofurantoin did not result in the modification of 3-nitrotyrosine in protein, peptide, or free amino acid. Stimulation of nfsA nfsB activity with paraquat had no effect on 3-nitrotyrosine reduction. Nonlethal exposure of E. coli to peroxynitrite/CO(2) resulted in the reproducible nitration of tyrosine residues in endogenous proteins. The degree of 3-nitrotyrosine immunoreactivity over the 2-h postexposure period did not differ between mutant and wild-type strains. These results indicate that the nfsA and nfsB enzymes do not reduce 3-nitrotyrosine.

Bacterial Proteins↗
PubMed2002

Flavin thermodynamics explain the oxygen insensitivity of enteric nitroreductases.

Bacterial nitroreductases are NAD(P)H-dependent flavoenzymes which catalyze the oxygen-insensitive reduction of nitroaromatics, quinones, and riboflavin derivatives. Despite their broad substrate specificity, their reactivity is very specific for two-electron, not one-electron, chemistry. We now describe the thermodynamic properties of the flavin mononucleotide cofactor of Enterobacter cloacae nitroreductase (NR), determined under a variety of solution conditions. The two-electron redox midpoint potential of NR is -190 mV at pH 7.0, and both the pH dependence of the midpoint potential and the optical spectrum of the reduced enzyme indicate that the transition is from neutral oxidized flavin to anionic flavin hydroquinone. The one-electron-reduced semiquinone states of both the free enzyme and an NR-substrate analogue complex are strongly suppressed based on optical spectroscopy and electron paramagnetic resonance measurements. This can explain the oxygen insensitivity of NR and its homologues, as it makes the execution of one-electron chemistry thermodynamically unfavorable. Therefore, we have established a chemical basis for the recent finding that a nitroreductase is a member of the soxRS oxidative defense regulon in Escherichia coli [Liochev, S. I., Hausladen, A., Fridovich, I. (1999) Proc. Natl. Acad. Sci. U.S.A. 96 (7), 3537-3539]. We also report binding affinities for the FMN cofactor in all three oxidation states either determined fluorometrically or calculated using thermodynamic cycles. Thus, we provide a detailed picture of the thermodynamics underlying the unusual activity of NR.

Apoenzymes↗
PubMed2005

Identification of aldehyde oxidase as the neonicotinoid nitroreductase.

Imidacloprid (IMI), the prototypical neonicotinoid insecticide, is used worldwide for crop protection and flea control on pets. It is both oxidatively metabolized by cytochrome P450 enzymes and reduced at the nitroguanidine moiety by a previously unidentified cytosolic "neonicotinoid nitroreductase", the subject of this investigation. Two major metabolites are detected on incubation of IMI with rabbit liver cytosol: the nitrosoguanidine (IMI-NO) and the aminoguanidine (IMI-NH2). Three lines of evidence identify the molybdo-flavoenzyme aldehyde oxidase (AOX, EC 1.2.3.1) as the neonicotinoid nitroreductase. First, classical AOX electron donor substrates (benzaldehyde, 2-hydroxypyrimidine, and N-methylnicotinamide) dramatically increase the rate of formation of IMI metabolites. Allopurinol and diquat are also effective electron donors, while NADPH and xanthine are not. Second, AOX inhibitors (potassium cyanide, menadione, and promethazine) inhibit metabolite formation when N-methylnicotinamide is utilized as an electron donor. Without the addition of an electron donor, rabbit liver cytosol reduces IMI only to IMI-NO at a slow rate. This reduction is also inhibited by potassium cyanide, menadione, and promethazine, as well as by additional AOX inhibitors, cimetidine and chlorpromazine. Finally, IMI nitroreduction by AOX is sensitive to an aerobic atmosphere, but to a much lesser extent than cytochrome P450 2D6. Large species differences are observed in the IMI nitroreductive activity of liver cytosol. While rabbit and monkey (Cynomolgus) give the highest levels of total metabolite formation, human, mouse, cow, and rat also metabolize IMI rapidly. In contrast, dog, cat, and chicken liver cytosols do not reduce IMI at appreciable rates. AOX, as a neonicotinoid nitroreductase, may limit the persistence of IMI, and possibly other neonicotinoids, in mammals.

Aldehyde Oxidase↗
PubMed1997

Azoreductase and nitroreductase activity of bacteria in feces from patients with an ileal reservoir.

Azoreductase and nitroreductase activities of bacteria in feces of five patients with ileal reservoirs were evaluated, both at the onset of symptoms of pouchitis and following recovery after treatment with drugs. All stool samples tested had bacteria with azoreductase and nitroreductase activities. Azoreductase and nitroreductase activities were higher after recovery than during attacks of pouchitis. During reestablishment of the normal microflora in the ileal reservoirs after pouchitis, the anaerobic bacteria increased and the aerobic bacteria decreased.

Bacteria↗
PubMed1997

The expression of bacterial nitroreductase in transgenic mice results in specific cell killing by the prodrug CB1954.

The enzyme nitroreductase, isolated from Escherichia coli B, converts CB1954 ((5-aziridin-1-yl)-2,4-dinitro-benzamide) into a cytotoxic DNA interstrand cross-linking agent. The E. coli B gene (nfnB, NTR) encoding nitroreductase (NTR) was cloned into eukaryotic expression vectors. When driven by a CMV promoter, 5-10% of the stably transfected mouse fibroblasts expressed the NTR enzyme. These cells were killed at a concentration of 20 microM CB1954 in comparison to nonexpressing cells which were killed at a much higher concentration (500 microM). We subsequently generated transgenic mice to test the prodrug system in vivo. Nitroreductase was expressed specifically in T cells driven by the control elements of the human CD2 locus. Upon CB1954 treatment, transgenic mice show extensive cell depletion in thymus and spleen (14-16% of normal cell numbers), whereas all other tissues are unaffected by prodrug administration. These results raise the possibility of using the NTR gene in anticancer therapy.

Animals↗
PubMed2001

Telomerase-specific suicide gene therapy vectors expressing bacterial nitroreductase sensitize human cancer cells to the pro-drug CB1954.

Telomerase activation is considered to be a critical step in cancer progression due to its role in cellular immortalization. The prevalence of telomerase expression in human cancers makes it an attractive candidate for new mechanism-based targets for cancer therapy. The selective killing of cancer cells can be achieved by gene-directed enzyme pro-drug therapy (GDEPT). In this study we have tested the feasibility of using the transcriptional regulatory sequences from the hTERT and hTR genes to regulate expression of the bacterial nitroreductase enzyme in combination with the pro-drug CB1954 in a suicide gene therapy strategy. hTERT and hTR promoter activity was compared in a panel of 10 cell lines and showed a wide distribution in activity; low activity was observed in normal cells and telomerase-negative immortal ALT cell lines, with up to 300-fold higher activity observed in telomerase positive cancer lines. Placing the nitroreductase gene under the control of the telomerase gene promoters sensitized cancer cells in tissue culture to the pro-drug CB1954 and promoter activity was predictive of sensitization to the pro-drug (2-20-fold sensitization), with cell death restricted to lines exhibiting high levels of promoter activity. The in vivo relevance of these data was tested using two xenograft models (C33a and GLC4 cells). Significant tumour reduction was seen with both telomerase promoters and the promoter-specific patterns of sensitization observed in tissue culture were retained in xenograft models. Thus, telomerase-specific suicide gene therapy vectors expressing bacterial nitroreductase sensitize human cancer cells to the pro-drug CB1954.

Animals↗
PubMed1989

Nitroreductase activity of NADH dehydrogenase of the respiratory redox chain.

1. An NADH-dependent nitroreductase from the inner membrane of ox liver mitochondria copurified with Complex I of the respiratory redox chain (NADH:ubiquinone oxidoreductase, EC 1.6.5.3). 2. The corresponding nitroreductase from ox heart mitochondria co-purified with the NADH-cytochrome c reductase of Mahler, Sarkar & Vernon [(1952) J. Biol. Chem. 199, 585-597] [NADH: (acceptor) oxidoreductase, EC 1.6.99.3], a component of Complex I that contains the FMN. 3. The mitochondrial nitroreductase activity is attributed to the flavoprotein component of Complex I.

Animals↗
PubMed2002

Structures of nitroreductase in three states: effects of inhibitor binding and reduction.

The crystal structure of the nitroreductase enzyme from Enterobacter cloacae has been determined for the oxidized form in separate complexes with benzoate and acetate inhibitors and for the two-electron reduced form. Nitroreductase is a member of a group of enzymes that reduce a broad range of nitroaromatic compounds and has potential uses in chemotherapy and bioremediation. The monomers of the nitroreductase dimer adopt an alpha+beta fold and together bind two flavin mononucleotide prosthetic groups at the dimer interface. In the oxidized enzyme, the flavin ring system adopts a strongly bent (16 degrees ) conformation, and the bend increases (25 degrees ) in the reduced form of the enzyme, roughly the conformation predicted for reduced flavin free in solution. Because free oxidized flavin is planar, the induced bend in the oxidized enzyme may favor reduction, and it may also account for the characteristic inability of the enzyme to stabilize the one electron-reduced semiquinone flavin, which is also planar. Both inhibitors bind over the pyrimidine and central rings of the flavin in partially overlapping sites. Comparison of the two inhibitor complexes shows that a portion of helix H6 can flex to accommodate the differently sized inhibitors suggesting a mechanism for accommodating varied substrates.

Crystallography, X-Ray↗
PubMed1987

The toxicity and mutagenicity of the anti-tumour drug 5-aziridino-2,4-dinitrobenzamide (CB1954) is greatly reduced in a nitroreductase-deficient strain of E. coli.

In the 1970s it was shown that the monofunctional alkylating agent CB1954 (5-aziridino-2,4-dinitrobenzamide) kills the Walker rat carcinoma 256 in vivo and in vitro, but is inactive against several other tumours. In studies with bacteria, the large differences in survival in DNA-repair-proficient and deficient strains of Escherichia coli B treated with CB1954 were characteristic of a difunctional cross-linking agent. It was concluded that DNA was the only target large enough to receive significantly more than one lethal hit per molecule and that mono-alkylation alone could not account for the lethal effects of CB1954. In 1986 it was shown that CB1954 induced DNA interstrand cross-links in CB1954-sensitive cultured Walker 256 cells, but not in resistant Chinese hamster V79 cells, suggesting that the sensitivity of Walker cells results mainly from their activation of the drug to a difunctional agent by nitroreduction. To test this, we assayed the toxicity and mutagenicity of CB1954 in nitroreductase-plus and -minus strains of E. coli WP2uvrA. Agar-overlay assays showed that CB1954 was mutagenic to several strains of E. coli WP2, in a dose range 1-100 micrograms per plate, with slopes (mutants/nmol) of 7.1, 1.05 and 0.16 for WP2uvrA pKM101, WP2uvrA and WP2. Assays with nitrofurazone showed that these strains possessed nitroreductase activity. However, E. coli NFR-343, a nitrofurazone-resistant mutant of WP2uvrA which lacks nitroreductase activity was markedly less sensitive to the mutagenicity of CB1954, giving a mean slope of 0.12 compared with 1.15 for WP2uvrA. Aroclor-induced rat-liver S9 did not change these responses.(ABSTRACT TRUNCATED AT 250 WORDS)

Antineoplastic Agents↗
PubMed2002

Bacillus amyloliquefaciens orthologue of Bacillus subtilis ywrO encodes a nitroreductase enzyme which activates the prodrug CB 1954.

A nitroreductase with distinct properties that can activate the prodrug 5-aziridinyl-2,4-dinitrobenzamide (CB 1954) was isolated from Bacillus amyloliquefaciens. The encoding gene was identified as a homologue of the ywrO of Bacillus subtilis, and was obtained as a PCR product by reverse genetics, cloned and the entire nucleotide sequence determined. The gene was found to reside between homologues of the B. subtilis alsD and yswB genes; however, the ywrO and yswB genes of B. amyloliquefaciens were not separated by a fourth gene, ywsA. The B. amyloliquefaciens ywrO gene was overexpressed, the recombinant protein purified and its properties were compared with those of two CB 1954-activating enzymes, Escherichia coli B nitroreductase (NTR) and Walker DT-diaphorase (DTD). In common with these enzymes menadione was an electron acceptor (K(m) 3 microM) and activity with this substrate was inhibited by the presence of dicoumarol (K(i) 1.0 microM). In contrast, YwrO showed a marked preference for NADPH as a cofactor (K(m) 40 microM) and therefore could not be classified as a DTD (EC 1.6.99.2). The flavin FMN was an acceptor with high affinity. B. amyloliquefaciens YwrO was shown to be a flavoprotein with a monomeric molecular mass of 21.5 kDa by calculation and SDS-PAGE. The cytotoxic 4-hydroxylamine derivative was the single CB 1954 reduction product, but B. amyloliquefaciens YwrO was inactive with the bischloroethyl analogue of CB 1954, SN 23862. In both of these properties B. amyloliquefaciens YwrO more closely resembles DTD than NTR. Its K(m) for CB 1954 was lower than that of NTR (617 microM compared to 862 microM). Enhanced in vitro cytotoxicity of CB 1954 was demonstrated on incubation of V79 cells with prodrug, NADPH and B. amyloliquefaciens YwrO. The work has led to the identification of a previously unknown nitroreductase, B. amyloliquefaciens YwrO, with distinct properties which will aid the rational selection of appropriate genes for applications in directed enzyme prodrug therapy (DEPT).

Amino Acid Sequence↗
PubMed2005

PnrA, a new nitroreductase-family enzyme in the TNT-degrading strain Pseudomonas putida JLR11.

Nitroreductases are a group of proteins that catalyse pyridine nucleotide-dependent reduction of nitroaromatics compounds, showing significant human health and environmental implications. In this study we have identified the nitroreductase-family enzymes PnrA and PnrB from the TNT-degrading strain Pseudomonas putida. The enzyme encoded by the pnrA gene was expressed in Escherichia coli, purified to homogeneity and shown to be a flavoprotein that used 2 mol of NADPH to reduce 1 mol of 2,4,6-trinitrotoluene (TNT) to 4-hydroxylamine-2,6-dinitrotoluene, using a ping-pong bi-bi mechanism. The PnrA enzyme also recognized as substrates as a number of other nitroaromatic compounds, i.e. 2,4-dinitrotoluene, 3-nitrotoluene, 3- and 4-nitrobenzoate, 3,5-dinitrobenzamide and 3,5-dinitroaniline expanding the substrates profile from previously described nitroreductases. However, TNT resulted to be the most efficient substrate examined according to the Vmax/Km parameter. Expression analysis of pnrA- and pnrB-mRNA isolated from cells growing on different nitrogen sources suggested that expression of both genes was constitutive and that its level of expression was relatively constant regardless of the growth substrate. This is in agreement with enzyme-specific activity determined with cells growing with different N-sources.

Amino Acid Sequence↗
PubMed1994

Physical characterisation of the Escherichia coli B gene encoding nitroreductase and its over-expression in Escherichia coli K12.

The Escherichia coli B gene (nfnB) encoding nitroreductase has been cloned in Escherichia coli K-12 and its nucleotide sequence determined. The translated amino acid sequence was found to share substantial identity (88.5%) with the equivalent proteins of Enterobacter cloacae and Salmonella typhimurium. When the structural gene was placed under the transcriptional control of either the trp or lac promoter, recombinant nitroreductase was accumulated to 33% and 25% of the cell's soluble protein, respectively. Substitution of the nfrB ribosome binding site with that of the E. coli lacZ gene reduced production levels of nitroreductase. The sequenced region also contained two incomplete open reading frames of unknown function.

Amino Acid Sequence↗