Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:1.7.1.4 (nitrite reductase)
 1,847 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A tobacco nitrite reductase (NiR) cDNA and its corresponding gene were isolated from cDNA and genomic libraries. An NiR antisense mRNA was expressed in transgenic tobacco under the control of a double 35S promoter. Transformants were obtained on a medium containing ammonium as the sole source of nitrogen. One plant growing normally on ammonium but displaying drastically reduced development and chlorotic leaves when grown on nitrate as the sole source of nitrogen was studied further. This plant accumulated nitrite fivefold over wild-type level and showed reduced amounts of ammonium (11% wild-type level), glutamine (19%), and total protein (8%). NiR mRNA and activity were below detectable levels. Under these conditions, nitrate reductase (NR) activity and mRNA were overexpressed, suggesting that N-metabolites resulting from nitrate reduction are responsible for the repression of the expression of the NR gene, independently from the presence or absence of a functional NR protein.
 ...
PMID:Inhibition of tobacco nitrite reductase activity by expression of antisense RNA. 128 56

nit-4 is a pathway-specific regulatory gene which controls nitrate assimilation in Neurospora crassa, and appears to mediate nitrate induction of nitrate and nitrite reductase. The NIT4 protein consists of 1090 amino-acid residues and possesses a single GAL4-like putative DNA-binding domain plus acidic, glutamine-rich, and polyglutamine regions. Several mutants with amino-acid substitutions in the putative DNA-binding domain and a nit-4 deletion mutant, which encodes a truncated NIT4 protein lacking the polyglutamine region, are functional, i.e., they are capable of transforming a nit-4 mutant strain. However, transformants obtained with most of these nit-4 mutant genes possess a markedly reduced level of nitrate reductase and grow only slowly on nitrate, emphasizing the need to examine quantitatively the affects of in vitro-manipulated genes. The possibility that some mutant genes could yield transformants only if multiple copies were integrated was examined. The presence of multiple copies of wild-type or mutant nit-4 genes did not generally lead to increased enzyme activity or growth rate, but instead frequently appeared to be detrimental to nit-4 function. A hybrid nit-4-nirA gene transforms nit-4 mutants but only allows slow growth on nitrate and has a very low level of nitrate reductase.
 ...
PMID:Transformants of Neurospora crassa with the nit-4 nitrogen regulatory gene: copy number, growth rate and enzyme activity. 138 9

nit-4, a pathway-specific regulatory gene in the nitrogen circuit of Neurospora crassa, is required for the expression of nit-3 and nit-6, the structural genes which encode nitrate and nitrite reductase, respectively. The complete nucleotide sequence of the nit-4 gene has been determined. The predicted NIT4 protein contains 1,090 amino acids and appears to possess a single Zn(II)2Cys6 binuclear-type zinc finger, which may mediate DNA binding. Site-directed mutagenesis studies demonstrated that cysteine and other conserved amino acid residues in this possible DNA-binding domain are necessary for nit-4 function. A stretch of 27 glutamines, encoded by a CAGCAA repeating sequence, occurs in the C terminus of the NIT4 protein, and a second glutamine-rich domain occurs further upstream. A NIT4 protein deleted for the polyglutamine region was still functional in vivo. However, nit-4 function was abolished when both the polyglutamine region and the glutamine-rich domain were deleted, suggesting that the glutamine-rich domain might function in transcriptional activation. The homologous regulatory gene from Aspergillus nidulans, nirA, encodes a protein whose amino-terminal half has approximately 60% amino acid identity with NIT4 but whose carboxy terminus is completely different. A hybrid nit-4-nirA gene was constructed and found to function in N. crassa.
 ...
PMID:nit-4, a pathway-specific regulatory gene of Neurospora crassa, encodes a protein with a putative binuclear zinc DNA-binding domain. 184 Jun 34

This report describes the isolation and characterization of a Neurospora crassa mutant with an impaired regulation of nitrate reductase. Glutamine, which prevents the induction of nitrate reductase in N. crassa, did so relatively ineffectively in this mutant. The mutation did not affect the regulation of all enzymes regulated by "nitrogen metabolite regulation"; it did affect the regulation of nitrate reductase, nitrite reductase, histidase, and acetamidase, as well as that of thiourea sensitivity. The mutation was not allelic with nit-2, the gene controlling a general positive effector of nitrogen metabolite-regulated enzyme formation.
 ...
PMID:Physiological characterization of a Neurospora crassa mutant with impaired regulation of nitrate reductase. 610 86

In Neurospora crassa, synthesis of the enzymes of nitrate assimilation, nitrate reductase and nitrite reductase, was repressed by the presence of ammonium, glutamate, or glutamine. This phenomenon was a manifestation of the regulatory process termed nitrogen metabolite repression whereby alternative pathways of nitrogen acquisition are not expressed in cells enjoying nitrogen sufficiency. However, the glutamine synthetase mutant gln-1b had derepressed levels of the nitrate assimilation enzymes. The inability of glutamine to achieve nitrogen metabolite repression in this mutant militated against its potential role as the direct effector of this regulation.
 ...
PMID:Effect of the gln-1b mutation on nitrogen metabolite repression in Neurospora crassa. 610 13

Neurospora crassa nmr-1 mutants, selected on the basis of their sensitivity to chlorate in the presence of glutamine, have elevated levels of the nitrate assimilation enzymes, NADPH-nitrate reductase and NAD(P)H-nitrite reductase. Immunoelectrophoretic determinations show that the higher nitrate reductase activities in nmr-1 mutants are due to greater enzyme concentrations. The half-life of nitrate reductase in these mutants is unaltered. As in wild-type, expression of nitrate assimilation in nmr-1 mutants is dependent on induction by nitrate. Reduced nitrogen metabolites like ammonium and glutamine still repress this expression in nmr-1 mutants, but not as effectively as in wild-type. Enzymatic activity measurements in double mutant strains confirm that the nit regulatory loci, nit-2 and nit-4/5, are epistatic to nmr-1, but nmr-1 is epistatic to nit-3, the nitrate reductase structural gene. The results imply that nmr-1 is involved in post-transcriptional control of nitrate assimilation.
 ...
PMID:The regulation of nitrate assimilation in Neurospora crassa: biochemical analysis of the nmr-1 mutants. 645 34

Two gentamicin-resistant mutants of Pseudomonas aeruginosa PAO 503 were selected after ethyl methane sulfonate mutagenesis. Mutant PAO 2403 had significantly increased resistance to aminoglycoside but not to other antibiotics. Mutant PAO 2402 showed a similar spectrum of resistance but of lower magnitude. Both mutants showed no detectable cytochrome d and had a high frequency of reversion to a fully wild-type phenotype. PAO 2403 had a marked decrease and PAO 2402 had a moderate decrease in nitrite reductase activity. Both mutants had reduced uptake of gentamicin and dihydrostreptomycin. Mutant PAO 2403 showed a general decrease in transport rate of cationic compounds, whereas mutant PAO 2402 had only deficient glucose transport. Both mutants showed enhanced rates of glutamine transport and no change in glutamic acid transport. Other components of electron transport and oxidative phosphorylation were normal. These mutants involve ferrocytochrome C551 oxidoreductase formed only on anaerobic growth but illustrate transport defects in aerobically grown cells.
 ...
PMID:Aminoglycoside-resistant mutants of Pseudomonas aeruginosa deficient in cytochrome d, nitrite reductase, and aerobic transport. 679 88

The Neurospora crassa assimilatory nitrite reductase structural gene, nit-6, has been isolated. A cDNA library was constructed from poly(A)+ RNA isolated from Neurospora mycelia in which nitrate assimilation had been induced. This cDNA was ligated into lambda ZAP II (Stratagene) and amplified. This library was then screened with a polyclonal antibody specific for nitrite reductase. A total of six positive clones were identified. Three of the six clones were found to be identical via restriction digests, restriction fragment length polymorphism mapping, Southern hybridization, and some preliminary sequencing. One of these cDNA clones (pNiR-3) was used as a probe in Northern assays and was found to hybridize to a 3.5-kb poly(A)+ RNA whose expression is nitrate inducible and glutamine repressible in wild-type mycelia. pNiR-3 was used to probe an N. crassa genomic DNA library in phage lambda J1, and many positive clones were isolated. When five of these clones were tested for their ability to transform nit-6 mutants, one clone consistently generated many wild-type transformants. The nit-6 gene has been subcloned to generate pnit-6. The nit-6 gene has been sequenced and mapped; its deduced amino acid sequence exhibits considerable levels of homology to the sequences of Aspergillus sp. and Escherichia coli nitrite reductases. Several pnit-6 transformants have been propagated as homokaryons. These strains have been assayed for the presence of multiple copies of the nit-6 gene, as well as nitrite reductase activity.
 ...
PMID:Molecular cloning, characterization, and nucleotide sequence of nit-6, the structural gene for nitrite reductase in Neurospora crassa. 809 40

Nitrate (NR) and nitrite reductase (NiR) catalyse the reduction of nitrate to ammonium. The regulation of NR and NiR gene expression by carbohydrates (C) and nitrogen (N) metabolites was studied using detached leaves. In the dark, glucose fructose and sucrose supplied to detached green leaves of dark-adapted Nicotiana plumbaginifolia plants resulted in NR mRNA and protein accumulation and the loss of circadian rhythmicity in the size of the transcript pool. The characterization of transgenic plants expressing either a NR cDNA controlled by the 35S CaMV promoter or a transcriptional fusion between the tobacco nia1 (NR structural gene) promoter and the beta-glucuronidase reporter gene, led us to conclude that C metabolite control is taking place at the transcriptional level. Under low light conditions (limiting photosynthetic conditions), the supply of glutamine or glutamate resulted in a drop in the level of NR mRNA. Exogenously supplied carbohydrates partially antagonized this inhibitory effect suggesting that the availability of N and C metabolites affects the expression of the NR gene. The effects of carbohydrates and glutamine on NiR expression were also studied. NiR mRNA levels in the dark were relatively insensitive to feeding with glucose. Glutamate and glutamine were less efficient at decreasing NiR mRNA than NR mRNA levels. In contrast to NR, NiR mRNA levels were significantly increased by light treatments, indicating that NiR display regulatory characteristics reminiscent of photosynthetic genes such as the small subunit of ribulose bisphosphate carboxylase than to NR.
 ...
PMID:Regulation of nitrate and nitrite reductase expression in Nicotiana plumbaginifolia leaves by nitrogen and carbon metabolites. 822 Apr 46

Eleven green individuals were isolated when 95000 M2 plants of barley (Hordeum vulgare L.), mutagenised with azide in the M1, were screened for nitrite accumulation in their leaves after nitrate treatment in the light. The selected plants were maintained in aerated liquid culture solution containing glutamine as sole nitrogen source. Not all plants survived to flowering and some others that did were not fertile. One of the selected plants, STA3999, from the cultivar Tweed could be crossed to the wild-type cultivar and analysis of the F2 progeny showed that leaf nitrite accumulation was due to a recessive mutation in a single nuclear gene, which has been designated Nir1. The homozygous nir1 mutant could be maintained to flowering in liquid culture with either glutamine or ammonium as sole nitrogen source, but died within 14 days after transfer to compost. The nitrite reductase cross-reacting material seen in nitrate-treated wild-type plants could not be detected in either the leaf or the root of the homozygous nir1 mutant. Nitrite reductase activity, measured with dithionite-reduced methyl viologen as electron donor, of the nitrate-treated homozygous nir1 mutant was much reduced but NADH-nitrate reductase activity was elevated compared to wild-type plants. We conclude that the Nir1 locus determines the formation of nitrite reductase apoprotein in both the leaf and root of barley and speculate that it represents either the nitrite reductase apoprotein gene locus or, less likely, a regulatory locus whose product is required for the synthesis of nitrite reductase, but not nitrate reductase.(ABSTRACT TRUNCATED AT 250 WORDS)
 ...
PMID:nir1, a conditional-lethal mutation in barley causing a defect in nitrite reduction. 843 74


1 2 3 4 5 Next >>