Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have selected alfalfa suspension cell lines that are 20- to 100-fold more resistant than wild-type cells to the nonselective herbicide L-phosphinothricin, a mixed competitive inhibitor of glutamine synthetase (GS). GS enzyme levels are three- to sevenfold elevated in the variant cell line. Partial amino acid sequences of two cyanogen bromide cleavage peptides have been determined on GS purified from the variant cell line and used to confirm the identity of a 276-base pair GS cDNA clone. Southern blot analysis of wild-type and variant cell DNAs using this cDNA as a probe indicate that resistance to L-phosphinothricin is a consequence of a four- to 11-fold amplification of one GS gene resulting in about an eightfold increase in mRNA levels, and an increased enzyme synthesis sufficient to overcome the toxic effects of the inhibitor.
J Mol Appl Genet 1984
PMID:Herbicide-resistant alfalfa cells: an example of gene amplification in plants. 615 83

Of the various eucaryotic tissues, where glutamine synthetase (GS) mRNA and its regulation have been investigated, the induction of GS by glucocorticoids in the embryonic chick retina represents one of the systems most extensively studied. GS mRNA was first identified at the polysomal level by immunochemical precipitation of fractionated polysomes containing nascent GS chains with anti-GS gamma-globulin. The mRNA has been shown to be polyadenylated at the 3' end; on this basis, it has been partially purified from embryonic chick retina as well as from N. Crassa by chromatography on oligo(dT)-cellulose or poly(U)-sepharose and translated in cell-free protein synthesizing systems derived from wheat germ. Hormonal regulation of GS activity studied in the embryonic retina, hepatoma tissue culture cells, or in other tissues is always shown to be mediated by GS mRNA. In the retina, hydrocortisone (HC) elicits an age-related and transcription-dependent induction of GS by enhancing the level of GS mRNA in the polysomes through an increased supply of this mRNA from the nucleus. Comparative studies of three inhibitors of transcription, viz. actinomycin D, leucanthone and proflavine on the induction of GS by HC indicate that the latter inhibits GS mRNA selectively and reversibly with minimal effects on other RNA synthesis. Since proflavine acts by competing with HC-receptor binding sites in the nuclei, further studies on its interaction with the retina genome are likely to help identify the DNA sequences involved in the GS induction. In bacteria, studies on the genetics and physiology of various mutants with lesions in the structural gene for GS show that the transcription of the GS gene (gln A) is regulated both positively and negatively by GS and the product of another gene gln F. Purification of GS mRNA to homogeneity cloning of its cDNA and development of assay systems for cell-free transcription of GS are other studies likely to advance our knowledge on GS mRNA and its regulation.
Mol Cell Biochem 1983
PMID:Messenger RNA for glutamine synthetase. Review article. 619 21

V79-56 cells have an absolute requirement for exogenous glutamine and are not inducible for glutamine synthetase. Prototrophs arise spontaneously at approximately 1.0 X 10(-5) per cell per generation as measured by fluctuation tests. Higher frequencies of glutamine-independent variants may be obtained by treatment with the mutagen ethyl methane sulfonate, as well as by exposure to 5-azacytidine and sodium butyrate, which act primarily by affecting gene expression. Variants of all types show marked elevation of glutamine synthetase activity. Although this activity declines toward constitutive levels in the presence of glutamine, it is still inducible in variant cells. These populations, after a lag, regain the ability for progressive growth in glutamine-free medium. Thus, the stable variation seen here is in the potential for induction, rather than steady-state expression of glutamine synthetase at a higher level.
Somat Cell Mol Genet 1984 May
PMID:Variants inducible for glutamine synthetase in V79-56 cells. 620 10

The influence of the relA1 mutation on the regulation of the ammonia assimilatory enzymes, glutamate dehydrogenase (EC 1.4.1.4), glutamine synthetase (EC 6.3.1.2), and glutamate synthase (EC 1.4.1.3), was examined. When cells grown in rich media (either Luria broth or glucose-ammonia plus casamino acids) were transferred to a glucose-ammonia medium, the relA mutant failed to resume growth and did not have the same increase in any of the assimilatory enzyme activities as the rel+ strain. This effect was particularly dramatic for glutamate dehydrogenase, which increased 6-fold in the rel+ strain. Measurements of the guanosine nucleotide concentrations showed that the rel+ strain had a ppGpp concentration about 9 times that of the relA mutant 5 min after the shift to minimal medium. These results are consistent with those for other biosynthetic enzymes and show that the ammonia assimilatory enzymes require a relA product for their synthesis during shift from rich to minimal media. In addition, we examined the response of these strains to a change in nitrogen source. The relA mutant again failed to resume growth after a shift from glucose-ammonia to glucose-arginine medium. Even though the ppGpp concentration did not increase, the rel+ strain grew and increased glutamine synthetase activities about 2-fold. These changes the absence of increased ppGpp levels suggest that some other relA-mediated function is important during this change in nitrogen source.
Mol Gen Genet 1982
PMID:The regulation of the ammonia assimilatory enzymes in Rel+ and Rel- strains of Salmonella typhimurium. 628 74

Some mutations to glutamine auxotrophy in the 86 unit region of the Salmonella chromosome lie within the nitrogen regulatory gene, ntrC, rather than the structural gene encoding glutamine synthetase, glnA, Assignment of mutations to ntrC is based on fine structure mapping by P22-mediated transduction and on complementation analysis. Strains with ntrC lesions that cause glutamine auxotrophy (NtrCrepressor) have very low levels of glutamine synthetase (lower than those of strains that completely lack ntrC function and comparable to those of strains that lack ntrA function). NtrCrep strains fail to increase synthesis of glutamine synthetase or several amino acid transport components under nitrogen limiting conditions. Thus, like ntrA strains, they appear to repress glnA transcription and fail to activate transcription of glnA or other nitrogen controlled genes. Mutations that suppress the glutamine requirement caused by NtrCrep lesions arise at high frequency; these mutations also suppress the glutamine requirement caused by ntrA lesions. Several suppressor mutations result in loss of function of ntrC.
Mol Gen Genet 1981
PMID:Glutamine auxotrophs with mutations in a nitrogen regulatory gene, ntrC, that is near glnA. 703 32

Cellular morphology, macromolecular composition, (DNA, RNA and Protein content) marker enzyme activities for neurons [neuron specific enolase (NSE)] and astrocytes [glutamine synthetase (GS)] and plasma membrane protein profiles in the bulk isolated neurons and astrocytes from control and ethanol treated rats were studied. One month aged Wistar rats were given ethanol as sole drinking fluid for 10 weeks. Scanning electron microscopy revealed a characteristic cell surface smoothening in astrocytes due to ethanol treatment. DNA levels were unaltered, while RNA and Protein contents were decreased in astrocytes and neurons. Further, 3H-leucine incorporation into proteins was decreased in neurons and astrocytes derived from ethanol treated rats indicating reduced protein synthesis in neurons and astrocytes. GS activity was affected severely suggesting impairment in astrocytic functions. Plasma membrane protein composition was analyzed by 2-D electrophoresis. The analysis indicated several protein defects in the plasma membranes of neurons and astrocytes, which might be involved in 'membrane disorder' during ethanol challenge. 125I-Wheat Germ agglutinin binding studies showed three prominent proteins (160, 116 and 97 kDa) in astrocyte membrane fraction suggesting the possible involvement of N-terminal glycoproteins in altered astrocyte morphology during ethanol ingestion. Impairment in the astrocyte cell functions, protein changes in plasma membrane and cellular morphology studies suggest that astrocytes may be more vulnerable than neurons for ethanol effects.
Mol Cell Biochem 1994 Jan 12
PMID:Differential changes in cell morphology, macromolecular composition and membrane protein profiles of neurons and astrocytes in chronic ethanol treated rats. 751 15

The cyanobacterial ntcA gene encodes a DNA-binding protein that belongs to the Crp family of bacterial transcriptional regulators. In this work, we describe the isolation of an ntcA insertional mutant of the dinitrogen-fixing, heterocyst-forming cyanobacterium Anabaena sp. PCC 7120. The Anabaena ntcA mutant was able to use ammonium as a source of nitrogen for growth, but was unable to assimilate atmospheric nitrogen (dinitrogen) or nitrate. Nitrogenase and enzymes of the nitrate reduction system were not synthesized in the ntcA mutant under derepressing conditions, and glutamine synthetase levels were lower in the mutant than in the wild-type strain. In the ntcA mutant, in response to removal of ammonium, accumulation of mRNA of the genes encoding nitrogenase (nifHDK), nitrite reductase (nir, the first gene of the nitrate assimilation operon), and glutamine synthetase (glnA) was not observed. A transcription start point of the Anabaena glnA gene (corresponding to RNAl), that has been shown to be used preferentially after nitrogen step-down, was not used in the ntcA insertional mutant. Heterocyst development (which is necessary for the aerobic fixation of dinitrogen) and induction of hetR (a regulatory gene that is required for heterocyst development) were also impaired in the ntcA mutant. These results showed that the ntcA gene product, NtcA, is required in Anabaena sp. PCC 7120 for the expression of genes encoding proteins involved in the assimilation of nitrogen sources alternative to ammonium including dinitrogen and nitrate, and that the process of heterocyst development is also controlled by NtcA.
Mol Microbiol 1994 Nov
PMID:Requirement of the regulatory protein NtcA for the expression of nitrogen assimilation and heterocyst development genes in the cyanobacterium Anabaena sp. PCC 7120. 753 71

Escherichia coli cells carrying the gltX351 allele are unable to grow at 42 degrees C (Ts phenotype) due to an altered glutamyl-tRNA synthetase. We found that gltX351 cells display a new phenotype termed Gsd-, i.e. an inability to raise glutamine synthetase activity above low constitutive levels in minimal medium with 6.8 mM glutamine as sole nitrogen source. When 0.5 mM NH4+ or 12 mM glutamate replaced glutamine, the glutamine synthetase activities of gltX351 cells were raised to wild-type levels. Northern experiments showed that the Gsd- phenotype is the result of an impairment in transcription initiation from the Ntr-regulated promoter, glnAp2. Intragenic and extragenic secondary mutations appeared frequently in gltX351 cells, which suppressed their Gsd- but not their Ts phenotype. Moreover, in heterozygous gltX+/gltX351 partial diploids, gltX351 was dominant for the Gsd- phenotype and recessive for the Tr phenotype. A slight increase in the glutamine pool and in the intracellular glutamine: 2-oxoglutarate ratio was also observed but this could not account for the Gsd- phenotype of gltX351 cells. In cells carrying gltX351 and a suppressor of the Gsd- phenotype, sup-1, tightly linked to gltX351, the glutamine pool and glutamine: 2-oxoglutarate intracellular ratio were even higher than in the gltX351 single mutant. These results indicate that the gltX351 mutant polypeptide may be the direct cause of the Gsd- phenotype. The possibility that it interacts with one or more components that trigger the Ntr response is discussed.
Mol Gen Genet 1993 Jun
PMID:Nitrogen regulation in an Escherichia coli strain with a temperature sensitive glutamyl-tRNA synthetase. 768 46

Recent studies in molecular evolution have generated strong conflicts in opinion as to how world living organisms should be classified. The traditional classification of life into five kingdom has been challenged by the molecular analysis carried out mostly on rRNA sequences, which supported the division of the extant living organisms into three major groups: Archaebacteria, Eubacteria, and Eukaryota. As to the problem of placing the root of the tree of life, the analysis carried out on a few genes has provided discrepant results. In order to measure the genetic distances between species, we have carried out an evolutionary analysis of the glutamine synthetase genes, which previously have been revealed to be good molecular clocks, and of the small and large rRNA genes. All data demonstrate that archaebacteria are more closely related to eubacteria than to eukaryota, thus supporting the classical division of living organisms into two main superkingdoms, Prokaryota and Eukaryota.
J Mol Evol 1995 Mar
PMID:Molecular classification of living organisms. 772 54

The glnA gene, encoding type I glutamine synthetase (GS) in Synechocystis sp. PCC 6803, showed a high sequence similarity with other cyanobacterial glnA genes. A dramatic decrease in the amount of glnA mRNA, a single transcript of about 1.6 kb, was observed after transfer to darkness, or after incubation with the electron transport inhibitors DCMU or DBMIB. The levels of glnA transcript were fully recovered after 5 min of reillumination. The glnA mRNA was found to be equally stable both in the light and the dark (half-life about 2.5 min). Unlike the glnA messenger, the amount of GS protein was not reduced in the dark. Synthesis of the glnA transcript in the dark required the presence of glucose. In addition, glnA transcription in a Synechocystis psbE-psbF mutant lacking photosystem II required the presence of glucose even when grown in the light. These observations indicate that glnA transcription is under the control of the redox state of the cell. Finally, nitrogen starvation provoked a delay in the decrease of glnA transcript in darkness, suggesting a connection between nitrogen and redox controls of glnA transcript levels.
Plant Mol Biol 1995 Feb
PMID:Electron transport controls transcription of the glutamine synthetase gene (glnA) from the cyanobacterium Synechocystis sp. PCC 6803. 772 55


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>