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Query: UMLS:C0519030 (Klebsiella)
 21,988 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The participation of tyramine oxidase in the regulation of arylsulfatase synthesis in Klebsiella aerogenes was studied. Arylsulfatase was synthesized when this organism was grown with methionine or taurine as the sulfur source (nonrepressing conditions) and was repressed by inorganic sulfate or cysteine; this repression was relieved by tyramine and related compounds (derepressing conditions). Under nonrepressing conditions, arylsulfatase synthesis was not regulated by tyramine oxidase synthesis. However, derepression of arylsulfatase and induction of tyramine oxidase synthesis by tyramine were both antagonized by glucose and other carbohydrate compounds. The derepressed synthesis of arylsulfatase, like that of tyramine oxidase, was released from catabolite repression by use of tyramine as the sole source of nitrogen. A mutant strain that exhibits constitutive synthesis of glutamine synthetase and high levels of histidase when grown in glucose-ammonium medium was subject to the catabolite repression of both tyramine oxidase and arylsulfatase syntheses. Mutants in which repression of arylsulfatase could not be relieved by tyramine could not utilize tyramine as the sole source of nitrogen and were defective in the gene for tyramine oxidase.
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PMID:Tyramine oxidase and regulation of arylsulfatase synthesis in Klebsiella aerogenes. 83 Jun 48

The cloning and sequence determination is reported of the DNA region of Rhizobium leguminosarum coding for glutamine synthetase II (GSII). An open reading frame (ORF) encoding 326 amino acids was defined as the glnII gene on the basis of its similarity to other glnII genes and the ability of a DNA fragment carrying this ORF to complement the glutamine auxotrophy of a Klebsiella pneumoniae glnA mutant. We find that the glnII gene in R. leguminosarum is transcribed as a monocistronic unit from a single promoter, which shows structural features characteristic of rpoN (ntrA)-dependent promoters. In K. pneumoniae, such promoters require the ntrC and rpoN (ntrA) gene products for transcription. The intracellular level of glnII mRNA changes when R. leguminosarum is grown on different nitrogen sources, as expected for regulation by the nitrogen regulatory system. Promoter deletion analysis has shown that an extensive upstream DNA sequence (316 bp) is essential for in vivo activation of the glnII promoter in different biovars of R. leguminosarum. This DNA region requires a wild-type ntrC gene for activity and includes two conserved putative NtrC-binding site sequences. The results conclusively show that transcription from the R. leguminosarum glnII promoter is fully dependent on positive control by NtrC protein and on an upstream activator sequence (UAS).
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PMID:Activation of the Rhizobium leguminosarum glnII gene by NtrC is dependent on upstream DNA sequences. 135 39

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

Using glnT DNA of Rhizobium meliloti as a hybridization probe we identified a R. leguminosarum biovar phaseoli (R. l. phaseoli) locus (glnT) expressing a glutamine synthetase activity in Klebsiella pneumoniae. A 2.2 kb DNA fragment from R. l. phaseoli was cloned to give plasmid pMW5a, which shows interspecific complementation of a K. pneumoniae glnA mutant. The cloned sequence did not show cross-hybridization to glnA or glnII, the genes coding for two glutamine synthetase isozymes of Rhizobium spp. While in previous reports on glnT of R. meliloti and Agrobacterium tumefaciens no glutamine synthetase activity was detected, we do find activity with the glnT locus of R. l. phaseoli. The glutamine synthetase (GSIII) activity expressed in a K. pneumoniae glnA strain from pMW5a shows a ratio of biosynthetic to transferase activity 10(3)-fold higher than that observed for GSI or GSII. GSIII is similar in molecular weight and heat stability to GSI.
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PMID:A previously unrecognized glutamine synthetase expressed in Klebsiella pneumoniae from the glnT locus of Rhizobium leguminosarum. 198 Jan 42

We have cloned and characterized three distinct Rhizobium meliloti loci involved in glutamine biosynthesis (glnA, glnII, and glnT). The glnA locus shares DNA homology with the glnA gene of Klebsiella pneumoniae, encodes a 55,000-dalton monomer subunit of the heat-stable glutamine synthetase (GS) protein (GSI), and complemented an Escherichia coli glnA mutation. The glnII locus shares DNA homology with the glnII gene of Bradyrhizobium japonicum and encodes a 36,000-dalton monomer subunit of the heat-labile GS protein (GSII). The glnT locus shares no DNA homology with either the glnA or glnII gene and complemented a glnA E. coli strain. The glnT locus codes for an operon encoding polypeptides of 57,000, 48,000, 35,000, 29,000, and 28,000 daltons. glnA and glnII insertion mutants were glutamine prototrophs, lacked the respective GS form (GSI or GSII), grew normally on different nitrogen sources (Asm+), and induced normal, nitrogen-fixing nodules on Medicago sativa plants (Nod+ Fix+). A glnA glnII double mutant was a glutamine auxotroph (Gln-), lacked both GSI and GSII forms, but nevertheless induced normal Fix+ nodules. glnT insertion mutants were prototrophs, contained both GSI and GSII forms, grew normally on different N sources, and induced normal Fix+ nodules. glnII and glnT, but not glnA, expression in R. meliloti was regulated by the nitrogen-regulatory genes ntrA and ntrC and was repressed by rich N sources such as ammonium and glutamine.
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PMID:Rhizobium meliloti 1021 has three differentially regulated loci involved in glutamine biosynthesis, none of which is essential for symbiotic nitrogen fixation. 256 98

The glnB gene from Bradyrhizobium japonicum, the endosymbiont of soybeans (Glycine max), was isolated and sequenced, and its expression was examined under various culture conditions and in soybean nodules. The B. japonicum glnB gene encodes a 12,237-dalton polypeptide that is highly homologous to the glnB gene products from Klebsiella pneumoniae and Escherichia coli. The gene is located directly upstream from glnA (encoding glutamine synthetase), a linkage not observed in enteric bacteria. The glnB gene from B. japonicum is expressed from tandem promoters, which are differentially regulated in response to the nitrogen status of the medium. Expression from the downstream promoter involves the B. japonicum ntrC gene product (NtrC) in both free-living and symbiotic cells. Thus, glnB, a putative nitrogen-regulatory gene in B. japonicum, is itself Ntr regulated, and NtrC is active in B. japonicum cells in their symbiotic state.
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PMID:Bradyrhizobium japonicum glnB, a putative nitrogen-regulatory gene, is regulated by NtrC at tandem promoters. 279 30

When suspensions of Klebsiella aerogenes are incubated in a nitrogen-free medium there is a gradual decrease in the levels of acid-precipitable protein and of aspartokinase III (lysine-sensitive) and aspartokinase I (threonine-sensitive) activities. In contrast, the level of glutamine synthetase increases slightly and then remains constant. Under these conditions, the glutamine synthetase and other proteins continue to be synthesized as judged by the incorporation of [14C]leucine into the acid-precipitable protein fraction and into protein precipitated by anti-glutamine synthetase antibodies, by the fact that growth-inhibiting concentrations of chloramphenicol also inhibit the incorporation of [14C]leucine into protein and into protein precipitated by anti-glutamine synthetase antibody, and by the fact that chloramphenicol leads to acceleration in the loss of aspartokinases I and III and promotes a net decrease in the level of glutamine synthetase and its cross-reactive protein. The loss of aspartokinases I and III in cell suspensions is stimulated by glucose and is inhibited by 2,4-dinitrophenol. Glucose also stimulates the loss of aspartokinases and glutamine synthetase in the presence of chloramphenicol. Cell-free extracts of K. aerogenes catalyze rapid inactivation of endogenous glutamine synthetase as well as exogenously added pure glutamine synthetase. This loss of glutamine synthetase is not associated with a loss of protein that cross-reacts with anti-glutamine synthetase antibodies. The inactivation of glutamine synthetase in extracts is not due to adenylylation. It is partially prevented by sulfhydryl reagents, Mn2+, antimycin A, 2,4-dinitrophenol, EDTA, anaerobiosis and by dialysis. Following 18 h dialysis, the capacity of extracts to catalyze inactivation of glutamine synthetase is lost but can be restored by the addition of Fe2+ (or Ni2+) together with ATP (or other nucleoside di- and triphosphates. After 40-60 h dialysis Fe3+ together with NADH (but not ATP) are required for glutamine synthetase inactivation. The results suggest that accelerated protein degradation in cells exposed to nitrogen-limited conditions reflects the differential destruction of some proteins, including aspartokinases I and III, in order to sustain the biosynthesis of others such as glutamine synthetase. The loss of glutamine synthetase activity in cell-free extracts is likely mediated in part by mixed-function oxidation systems and could represent a 'marking' step in protein turnover.
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PMID:Regulation of glutamine synthetase, aspartokinase, and total protein turnover in Klebsiella aerogenes. 286 82

The glutamine synthetase (GS) gene glnA of Thiobacillus ferrooxidans was cloned on recombinant plasmid pMEB100 which enabled Escherichia coli glnA deletion mutants to utilize (NH4)2SO4 as the sole source of nitrogen. High levels of GS-specific activity were obtained in the E. coli glnA deletion mutants containing the T. ferrooxidans GS gene. The cloned T. ferrooxidans DNA fragment containing the glnA gene activated histidase activity in an E. coli glnA glnL glnG deletion mutant containing the Klebsiella aerogenes hut operon. Plasmid pMEB100 also enabled the E. coli glnA glnL glnG deletion mutant to utilize arginine or low levels of glutamine as the sole source of nitrogen. There was no detectable DNA homology between the T. ferrooxidans glnA gene and the E. coli glnA gene.
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PMID:Cloning and expression of the Thiobacillus ferrooxidans glutamine synthetase gene in Escherichia coli. 286 77

The ntrA, ntrB and ntrC products are responsible for regulating the transcription of many genes involved in the assimilation of poor nitrogen sources in enteric bacteria. The presence of a similar system in the non-enteric bacterium Azotobacter vinelandii is reported here. Genes analogous to ntrA and ntrC were isolated from an A. vinelandii gene library by complementation of Escherichia coli mutants. The gene encoding glutamine synthetase, glnA, was also isolated and found to be adjacent to ntrC but distant from ntrA, as it is in enteric organisms. The cloned Azotobacter genes also complemented Klebsiella pneumoniae mutants and hybridized to K. pneumoniae ntrA, ntrC and glnA gene probes. The role of ntrA and ntrC in A. vinelandii was established by using Tn5 insertions in the cloned genes to construct mutants by marker exchange. These mutants show that both ntrA and ntrC are required for the utilization of nitrate as a nitrogen source. However, ntrC is not required for nitrogen fixation by A. vinelandii, in contrast with K. pneumoniae where both ntrA and ntrC are essential.
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PMID:Regulation of nitrogen metabolism in Azotobacter vinelandii: isolation of ntr and glnA genes and construction of ntr mutants. 287 49

We have demonstrated that Rhizobium leguminosarum strain LPR1105 contains a heat stable and a heat labile glutamine synthetase (EC 6.3.1.2) activity similar to those described for other Rhizobiaceae. Most of the activity is heat stable when this strain is grown on glutamine as sole nitrogen source, but most is heat labile when grown on nitrate. Using a gene bank of R. leguminosarum DNA we have isolated two clones, which code for heat stable (p7D9) and heat labile (p4F7) glutamine synthetase activity, by complementing the glutamine auxotrophy of Klebsiella pneumoniae glnA mutants. Cross-hybridization of p7D9 with a fragment of the glnA gene of K. pneumoniae was observed, but no cross-hybridization between p7D9 and p4F7 was found. Since these two regions hybridize to genomic DNA of R. leguminosarum they are probably the structural genes for GSI and GSII, and the availability of these genes will make it possible to test this hypothesis. Clone p4F7 complements an ntrC+ but not an ntrC K. pneumoniae glnA mutant, suggesting that the ntrC gene is required for the complementation of the glutamine auxotrophy by this plasmid.
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PMID:Characterization and cloning of two Rhizobium leguminosarum genes coding for glutamine synthetase activities. 287 69


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