A mutation leading to the total lack of nitrite reductase activity in Escherichia coli K 12

Chippaux, Marc; Giudici, D.; Abou-Jaoudé, A.; Casse, Francine; Pascal, Marie-Claire

doi:10.1007/bf00267485

Cited by 93 publications

(46 citation statements)

References 21 publications

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“…The anaerobic respiratory chains associated with these electron acceptors are generally inducible and are repressed during aerobic growth even in the presence of their inducer (for a general review see Ingledew & Poole, 1984). In addition, synthesis of the reductases (fumarate reductase, nitrate reductase and nitrite reductase) and other components of these respiratory systems depends on the regulatory locus fnr (Lambden & Guest, 1976;Newman & Cole, 1978;Chippaux et al, 1978). Evidence has accumulated to indicate that thefnr gene product (FNR) is a transcriptional activator which regulates the expression of its target genes in response to anaerobiosis.…”

Section: Introductionmentioning

confidence: 99%

Regulation and Over-expression of the fnr Gene of Escherichia coli

1987

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3279The fnr gene of Escherichia coli encodes a transcriptional activator (FNR) which is required for the expression of a number of genes involved in anaerobic respiratory pathways. From the study of a translational fusion of fnr to the gene for /3-galactosidase (ZacZ) it has been concluded that the fnr gene is expressed under both aerobic and anaerobic conditions and is subject to autoregulation and repression by glucose, particularly during anaerobic growth. These findings imply that during anaerobiosis the FNR protein adopts an active conformation, in which it functions both as a repressor of'the fnr gene and as an activator offitr-dependent genes. Sequences in the 5' non-coding region of fnr which could be involved in autoregulation are discussed. The fnr coding region was cloned into an expression vector which has allowed an amplification of FNR synthesis such that it accounts for about 2% of total cell protein. The ability to over-produce FNR in this way should be very useful for future biochemical studies.

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Section: Introductionmentioning

confidence: 99%

Regulation and Over-expression of the fnr Gene of Escherichia coli

1987

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“…The operon is positively controlled by an activator protein encoded by the closely linked narL gene and responding to nitrate as the inducer (38,39). The narC operon is inducible only anaerobically, and its expression also depends on the pleiotropic activator protein encoded by fnr at minute 29 (6,23). Fumarate reductase is encoded by the frdABCD operon at minute 94 (8,9,12,21,24,36).…”

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confidence: 99%

“…The frd operon is induced anaerobically by fumarate in the absence of nitrate (7,13,16,21,23). Expression of the operon also depends on the Fnr protein (6,23).…”

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Molybdenum effector of fumarate reductase repression and nitrate reductase induction in Escherichia coli

Iuchi¹,

Lin²

1987

J Bacteriol

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In Escherichia coli the presence of nitrate prevents the utilization of fumarate as an anaerobic electron acceptor. The induction of the narC operon encoding the nitrate reductase is coupled to the repression of the frd operon encoding the fumarate reductase. This coupling is mediated by nitrate as an effector and the narL product as the regulatory protein (S. Iuchi and E. C. C. Lin, Proc. Natl. Acad. Sci. USA 84:3901-3905, 1987).The protein-ligand complex appears to control narC positively butfrd negatively. In the present study we found that a molybdenum coeffector acted synergistically with nitrate in the regulation of frd and narC. In chlD mutants believed to be impaired in molybdate transport (or processing), full repression of I(frd-lac) and full induction of @(narC-lac) by nitrate did not occur unlesshe growth medium was directly supplemented with molybdate (1 ,uM). This requirement was not clearly m*iifested in wild-type cells, apparently because it was met by the trace quantities of molybdate present as a contaminant in the mineral medium. In chLB mutants, which are known to accumulate the Mo cofactor because of its failure to be inserted as a prosthetic group into proteins such as nitrate reductase, nitrate repression of frd and induction of narC were also intensified by molybdate supplementation. In this case a deficiency of the molybdenum coeffector might have resulted from enhanced feedback inhibition of molybdate transport (or processing) by the elevated level of the unutilized Mo cofactor. In addition, mutations in chlE, which are known to block the synthesis of the organic moiety of the Mo cofactor, lowered the threshold concentrations of nitrate (<1 ,uM) necessary for frd repression and narC induction. These changes could be explained simply by the higher intracellular nitrate attainable in cells lacking the ability to destroy the effector.

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“…Dr M.-C. Pascal of the Laboratoire de Chimie Bacterienne, CNRS, Marseille, France, kindly supplied the E. coli hydrogenase mutants isolated in that laboratory (Pascal et af., 1975;Chippaux et al, 1978). These strains (CB320, CB850, CB22, CB23) require threonine and leucine for growth and were grown on the above media supplemented with 0.2% (w/v) Casamino acids (Difco).…”

Section: E T H O D Smentioning

confidence: 99%

“…The mutants obtained here could be divided into four classes (A to D), and these were compared with the CB mutants (Pascal et a/., 1975;Chippaux et a!., 1978).…”

Section: R E S U L T Smentioning

confidence: 99%

Mutants of Escherichia coli with Altered Hydrogenase Activity

Krasna

1984

Microbiology

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Mutant strains of Escherichia coli which expressed different levels of hydrogenase activity when grown anaerobically under a variety of conditions were obtained by mutagenesis and selective growth and screening procedures. Four classes of mutants were isolated, ranging from those devoid of enzyme activity to those expressing maximal activity under all growth conditions. One class of mutants (A) could not grow on fumarate plus H 2 in the presence of active fumarate reductase. Since hydrogenase is essential for growth under these conditions some of these strains may be hydrogenase-negative. Three other classes of mutants were isolated which were all hydrogenase-positive and fully expressed this activity when grown on fumarate plus H 2 . They differed in the level of expression of hydrogenase activity when grown anaerobically on glucose, conditions which do not require hydrogenase for growth. Class B mutants expressed less activity, while class C mutants expressed more activity than the parental strain. Class D mutants fully expressed hydrogenase activity and were dependent on the enzyme for growth. The different strains were also assayed for reduction of dyes by hydrogen and for evolution of hydrogen from reduced methyl viologen. Some of the hydrogenase-positive strains showed altered activities in these assays suggesting that mutations may have occurred either in enzymes or proteins required for reaction with dyes or in the hydrogenase enzyme itself.

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A mutation leading to the total lack of nitrite reductase activity in Escherichia coli K 12

Cited by 93 publications

References 21 publications

Regulation and Over-expression of the fnr Gene of Escherichia coli

Regulation and Over-expression of the fnr Gene of Escherichia coli

Molybdenum effector of fumarate reductase repression and nitrate reductase induction in Escherichia coli

Mutants of Escherichia coli with Altered Hydrogenase Activity

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