Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.7.1.2 (nitrate reductase)
 3,861 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The nirA gene of Aspergillus nidulans and the nit-4 gene of Neurospora crassa appear to be equivalent pathway-specific regulatory genes which mediate nitrate induction of nitrate reductase and nitrite reductase (NR and NiR) activities. We have transformed the nit-4 wild-type (wt) gene into the A. nidulans loss-of-function (pleiotropic negative) nirA 1 mutant strain. The nit-4 gene was found to complement the nirA 1 mutation, thus permitting the nirA 1 mutant strain to grow on nitrate or nitrite as the sole source of nitrogen. Integration of the nit-4 gene in transformants appears to have occurred at a number of 'ectopic', i.e. non-nirA, sites. Nitrate is required for the induction of NR activity in nit-4-transformed strains whilst NR production remains markedly subject to nitrogen-metabolite repression. However, NR levels are modestly higher than wt under all growth conditions.
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PMID:Heterologous expression and regulation of the Neurospora crassa nit-4 pathway-specific regulatory gene for nitrate assimilation in Aspergillus nidulans. 182 47

A positive, genetic selection against the activity of the nitrogen regulatory (NTR) system was used to isolate insertion mutations affecting nitrogen regulation in Klebsiella aerogenes. Two classes of mutation were obtained: those affecting the NTR system itself and leading to the loss of almost all nitrogen regulation, and those affecting the nac locus and leading to a loss of nitrogen regulation of a family of nitrogen-regulated enzymes. The set of these nac-dependent enzymes included histidase, glutamate dehydrogenase, glutamate synthase, proline oxidase, and urease. The enzymes shown to be nac independent included glutamine synthetase, asparaginase, tryptophan permease, nitrate reductase, the product of the nifLA operon, and perhaps nitrite reductase. The expression of the nac gene was itself highly nitrogen regulated, and this regulation was mediated by the NTR system. The loss of nitrogen regulation was found in each of the four insertion mutants studied, showing that loss of nitrogen regulation resulted from the absence of nac function rather than from an altered form of the nac gene product. Thus we propose two classes of nitrogen-regulated operons: in class I, the NTR system directly activates expression of the operon; in class II, the NTR system activates nac expression and the product(s) of the nac locus activates expression of the operon.
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PMID:Role of the nac gene product in the nitrogen regulation of some NTR-regulated operons of Klebsiella aerogenes. 197 23

The nucleotide sequence of the Aspergillus nidulans crnA gene for the transport of the anion nitrate has been determined. The crnA gene specifies a predicted polypeptide of 483 amino acids (molecular weight 51,769). A hydropathy plot suggests that this polypeptide has 10 membrane-spanning helices with an extensive hydrophilic region between helices six and seven. No striking homology was observed between the crnA protein and other reported membrane proteins of either prokaryotic or eukaryotic organisms, indicating that the crnA transporter may represent another class of membrane protein. Northern blotting results with wild-type cells show that (i) control of crnA expression is subject to nitrate (and nitrite) induction as well as nitrogen metabolite repression and (ii) regulation of the crnA gene is exerted at the level of mRNA accumulation, most likely at transcription, in response to the nitrogen source in the growth medium. Furthermore, similar studies with mutants of nirA and areA control genes and the niaD nitrate reductase structural gene show that crnA expression is mediated by the products of nirA (nitrate induction control gene), areA (nitrogen metabolite repression control gene), and niaD (involved in autoregulation of nitrate reductase).
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PMID:crnA encodes a nitrate transporter in Aspergillus nidulans. 198 67

A transformation system for Gibberella fujikuroi based on the Aspergillus niger nitrate reductase gene (niaD) was developed. A strain (designated SG140) carrying a non-reverting niaD mutation (niaD11) was generated by screening mutagenised cells for non-growth on nitrate as sole nitrogen source. Transformation frequencies of 1-2 transformants per microgram DNA were observed when strain SG140 was transformed to nitrate utilisation. Southern blot analyses of niaD+ transformants showed that the vector DNA sequences were integrated into the chromosomal DNA. The results demonstrate that the A. niger niaD gene is expressed in G. fujikuroi.
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PMID:Transformation of the filamentous fungus Gibberella fujikuroi using the Aspergillus niger niaD gene encoding nitrate reductase. 200 64

Intragenic complementation has been observed between apoenzyme nitrate reductase-deficient mutants (nia) of Nicotiana plumbaginifolia. In vivo as in vitro, the NADH-nitrate reductase (NR) activity in plants heterozygous for two different nia alleles was lower than in the wild type plant, but the plants were able to grow on nitrate as a sole nitrogen source. NR activity, absent in extracts of homozygous nia mutants was restored by mixing extracts from two complementing nia mutants. These observations suggest that NR intragenic complementation results from either the formation of heteromeric NR or from the interaction between two modified enzymes. Complementation was only observed between mutants retaining different partial catalytic activities of the enzyme. Results are in agreement with molecular data suggesting the presence of three catalytic domains in the subunit of the enzyme.
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PMID:Genetic and biochemical analysis of intragenic complementation events among nitrate reductase apoenzyme-deficient mutants of Nicotiana plumbaginifolia. 201 42

By using a method in which cell-wall-deficient Chlamydomonas reinhardtii cells were agitated in the presence of DNA, glass beads, and polyethylene glycol, nuclear transformation rates of approximately 10(3) transformants per micrograms of plasmid DNA were achieved. The nitrate reductase gene from wild-type Chlamydomonas was used to complement a mutation in the corresponding gene of a strain containing nit1-305. Transformants were selected by growth with nitrate as sole source of nitrogen. The transforming DNA integrated into the genome at a low-copy number in nit+ transformants. When cells carrying nit1-305 were agitated in the presence of two plasmids, one with the gene for nitrate reductase and the second with an unselected gene, the unselected gene was present in 10-50% of nit+ transformants. This high frequency of cotransformation will allow any cloned gene to be introduced into Chlamydomonas. Moreover, the overall efficiency of transformation should be high enough to permit isolation of genes from genomic libraries by complementation of stable nuclear mutants. The availability of efficient nuclear and chloroplast transformation in Chlamydomonas provides specific advantages for the study of chloroplast biogenesis, photosynthesis, and nuclear-chloroplast genome interactions.
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PMID:High-frequency nuclear transformation of Chlamydomonas reinhardtii. 210 99

In Neurospora crassa limitation for single amino acids normally results in increased formation of enzymes required for amino acid synthesis via 'general amino acid control'. Glutamine limitation, however, led to comparatively low and delayed derepression of enzyme synthesis. Nitrate reductase activity increased steeply under these conditions confirming that de novo protein synthesis could occur. Derepression levels were unaffected by addition of glutamine-derived metabolites. Only small and delayed increases in mRNA levels occurred for the anabolic enzyme genes arg-12, his-3 and trp-1 under conditions of glutamine limitation in contrast to the immediate and far larger increase found on histidine limitation. The trans-acting regulatory gene of general amino acid control in Neurospora, cpc-1, responded with a significant increase in mRNA level to histidine and to glutamine limitation. The restricted response of the amino acid synthesis genes could imply a post-transcriptional block to the positive regulatory function of cpc-1 under condition of glutamine limitation. The results suggest that the expression of general amino acid control is restricted under conditions of inadequate nitrogen supply.
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PMID:Restricted activation of general amino acid control under conditions of glutamine limitation in Neurospora crassa. 214 7

The major nitrogen-regulatory gene nit-2 of Neurospora crassa activates the expression of numerous unlinked structural genes which specify nitrogen-catabolic enzymes during conditions of nitrogen limitation. The nit-2 gene encodes a regulatory protein of 1036 amino acid residues with a single 'zinc finger' and a downstream basic region, which together may constitute a DNA-binding domain. The zinc finger domain of the NIT2 protein was synthesized in vitro and also expressed as a fusion protein in Escherichia coli to examine its DNA-binding activity. The wild-type NIT2 finger domain protein binds to the promoter region of nit-3, the nitrate reductase structural gene. A series of NIT2 mutant proteins obtained by site-directed mutagenesis was expressed and tested for functional activity. The results demonstrate that both the single zinc-finger motif and the downstream basic region of NIT2 are critical for its trans-activating function in vivo and specific DNA-binding in vitro.
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PMID:Site-directed mutagenesis of the 'zinc finger' DNA-binding domain of the nitrogen-regulatory protein NIT2 of Neurospora. 215 May 39

Nitrate and nitrite was reduced by Escherichia coli E4 in a L-lactate (5 mM) limited culture in a chemostat operated at dissolved oxygen concentrations corresponding to 90-100% air saturation. Nitrate reductase and nitrite reductase activity was regulated by the growth rate, and oxygen and nitrate concentrations. At a low growth rate (0.11 h-1) nitrate and nitrite reductase activities of 200 nmol.mg-1 protein.min-1 and 250 nmol.mg-1 protein.min-1 were measured, respectively. At a high growth rate (0.55 h-1) both enzyme activities were considerably lower (25 and 12 nmol mg-1.protein.min-1). The steady state nitrite concentration in the chemostat was controlled by the combined action of the nitrate and nitrite reductase. Both nitrate and nitrite reductase activity were inversely proportional to the growth rate. The nitrite reductase activity decreased faster with growth rate than the nitrate reductase. The chemostat biomass concentration of E. coli E4, with ammonium either solely or combined with nitrate as a source of nitrogen, remained constant throughout all growth rates and was not affected by nitrite concentrations. Contrary to batch, E. coli E4 was able to grow in continuous cultures on nitrate as the sole source of nitrogen. When cultivated with nitrate as the sole source of nitrogen the chemostat biomass concentration is related to the activity of nitrate and nitrite reductase and hence, inversely proportional to growth rate.
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PMID:Aerobic nitrate and nitrite reduction in continuous cultures of Escherichia coli E4. 219 29

Genomic clones containing the entire crnA-niiA-niaD gene cluster of Aspergillus nidulans have been isolated, and the structures of the niiA and niaD genes have been determined by nucleotide sequence analysis. This gene cluster is required for the assimilation of nitrate in A. nidulans, and the three genes encode a product required for nitrate uptake and the enzymes, nitrite reductase and nitrate reductase, respectively. The putative coding sequences, as deduced by comparison to cDNA clones of both niiA and niaD, are interrupted by multiple small introns, and the two genes are divergently transcribed. Identification and characterization of specific mRNAs involved in nitrate assimilation indicates that only monocistronic transcripts are involved, and that the approximate sizes of these transcripts are 1.6 kb, 3.4 kb and 2.8 kb for crnA, niiA and niaD, respectively. The results also indicate that control of niiA and niaD gene expression is mediated by the levels of mRNA accumulation, in response to the source of nitrogen in the growth medium. Two types of transcripts for niiA were observed.
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PMID:Isolation and characterisation of the crnA-niiA-niaD gene cluster for nitrate assimilation in Aspergillus nidulans. 220 30


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