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)

The physiological roles of the gene subset defined by early-blocked sporulation mutations (spo0) and their second-site suppressor alleles (rvtA11 and crsA47) remain cryptic for both vegetative and sporulating Bacillus subtilis cells. To test the hypothesis that spo0 gene products affect global regulation, we assayed the levels of carbon- and nitrogen-sensitive enzymes in wild-type and spo0 strains grown in a defined minimal medium containing various carbon and nitrogen sources. All the spo0 mutations (except spo0J) affected both histidase and arabinose isomerase levels in an unexpected way: levels of both carbon-sensitive enzymes were two- to six-fold higher in spo0 strains compared to wild type, when cells were grown on the derepressing carbon sources arabinose or maltose. There was no difference in enzyme levels with glucose-grown cells, nor was there a significant difference in levels of the carbon-independent enzymes glutamine synthetase and glucose-6-phosphate dehydrogenase. This effect was not due to a slower growth rate for the spo0 mutants on the poor carbon and nitrogen sources used. The levels of carbon-sensitive enzymes were not simply correlated with sporulation ability in genetically suppressed spo0 mutants, but the rvtA and crsA suppressors each had such marked effects on wild-type growth and enzyme levels that these results were difficult to interpret. We conclude that directly or indirectly the spo0 mutations, although blocking the sporulation process, increase levels of carbon-sensitive enzymes, possibly at the level of gene expression.
Mol Gen Genet 1988 May
PMID:Early-blocked sporulation mutations alter expression of enzymes under carbon control in Bacillus subtilis. 313 15

The metabolism of thyroxine (T4) by cultures of embryonic-rat brain cells grown in a chemically defined medium was studied. Cells in these cultures were predominantly neurons, characterized by the developmental increase of the binding of [3H]flunitrazepam to the high-affinity (0.67 nM) benzodiazepine neuronal receptors. The cultures also contained astrocytes, characterized by immunological studies using an anti-glial fibrillary acidic protein (GFAp) and by the increase in glutamine synthetase (GS). Incubation of the cells, in situ, with 125I-labelled 3,5,3'-triiodothyronine (T3) showed the presence of a single class of high-affinity nuclear receptors for T3 with a maximal binding capacity of 270-470 fmol T3/mg DNA and a Kd of 63 +/- 13 pM. Cells incubated in situ with 50 pM [125I]T4 actively metabolized the hormone. The major metabolite, 3,3',5'-triiodothyronine (rT3) (159 +/- 43 fmol/4 h/mg DNA), was almost completely released into the medium. T3 was a minor metabolite (77 +/- 3 fmol/4 h/mg DNA), 75% of which accumulated in the cells. Of this T3, 35% was bound to the nuclear receptors after 4 h of incubation. In vitro assays showed that the 5'-deiodinase activity increased during culture and the 5-deiodinase decreased slightly. Cytosine-arabinoside (ARAc) treatment of the cultures reduced the DNA content per culture dish, corresponding to a fall in the number of GFAp-positive cells (astrocytes) and to a decrease in GS. A small increase in the number of benzodiazepine sites was observed. ARAc treatment markedly reduced the T3 production (14.5 +/- 0.7 fmol/4 h/mg DNA) and did not change the rT3 production. We suggest that T4 is metabolized to T3 in astrocytes, taken up by neurons and binds to their nuclear receptors.
Mol Cell Endocrinol 1988 Jul
PMID:Thyroid hormone metabolism in neuron-enriched primary cultures of fetal rat brain cells. 320 89

The metabolism of thyroxine (T4) and triiodothyronine (T3) in cultured glial cells was studied in situ. Cultures were prepared from fetal rat brain and grown for the last 4 days in a chemically defined medium (CDM). They contained astrocytes and oligodendrocytes as shown by the enzyme markers, glutamine synthetase and 2',3'-cyclic nucleotide phosphohydrolase. These cells contained high affinity (22-33 pM), limited capacity (120-230 fmol/mg DNA) nuclear receptors for T3. Cells incubated in situ with 50 pM [125I]T4 actively metabolized the hormone. The major iodothyronine produced was T3 (220-570 fmol/4 h/mg DNA). About 70% accumulated in the cells, the remainder was released into the medium. Within the cells, T3 was partly bound to the nuclear receptors (16.5-20 fmol/mg DNA). Reverse T3 (rT3) was a minor metabolite (30-45 fmol/4 h/mg DNA); it was almost completely released into the medium. The half-life of [125I]T3 (50 pM) was found to be about 15 h. These results show that, in situ, glial cell cultures containing astrocytes and oligodendrocytes grown in CDM actively deiodinate T4 to T3 and degrade T3 rather slowly.
Mol Cell Endocrinol 1986 Dec
PMID:Thyroid hormone metabolism by glial cells in primary culture. 380 6

The glutamine synthetase (GS) activity in Escherichia coli is regulated by a bicyclic interconvertible enzyme cascade which involves the cyclic adenylylation (inactivation) and deadenylylation (activation) of GS on the one hand, and the modulation of these processes by the uridylylation and deuridylylation of Shapiro's regulatory protein on the other. The specific activity of GS in a given metabolic state is determined by the fraction of its subunits that are adenylylated, and this fraction is determined by the concentration of over 40 metabolites. Through allosteric and substrate interactions with one or more of the cascade enzymes, these metabolites alter the rates of the covalent modification and demodification reactions. By means of immunoprecipitation studies with anti-AMP specific antibodies, it has been established that the partially adenylylated glutamine synthetase, which is present in a given steady state, is a mixture of hybrid molecules containing different numbers and possibly distributions of adenylylated subunits. Partial separation of these hybrid mixtures has been achieved by affinity chromatography on Affi-Blue Sepharose columns. From immunochemical studies it is evident that anti-AMP antibodies can react with adenylylated subunits of all molecular species of GS, but that the capacities of these primary antigen-antibody reactions to yield precipitable aggregates is very dependent of the number of adenylylated subunits per molecule, and much less so upon the total concentration of adenylylated subunits present. the studies suggest that precipitability is a function either of the distribution of adenylylated subunits within hybrid species, or of the kinetics of intra- vs intermolecular bivalent interactions.
Mol Biol Biochem Biophys 1980
PMID:Subunit interaction of adenylylated glutamine synthetase. 610

Growth of Neurospora crassa on media containing NH4+ leads to the repression of a variety of permeases and alternative pathways which would generate NH4+, so called "ammonium repression." The mutant am2 which lacks NADP-GDH is not subject to ammonium repression of nitrate reductase or urea permease, but like the wild type has repressed levels of these systems when grown in the presence of proline, glutamate or glutamine. The glutamine synthetase (GS) mutant gln-1a has derepressed levels of the aforementioned systems unless grown with glutamine. The oligomeric state of GS depends upon the nitrogen sufficiency of the cell, a tetrameric form predominates under conditions of nitrogen limitation and an octameric form under conditions of nitrogen sufficiency. We have found that the tetrameric form GS predominates in the mutants am2 and gln-1a when they are ammonium derepressed. Th mechanism of NH4+ repression in N. crassa is thought to entail a cessation of positive gene action by the product of the nit-2 regulatory gene. We propose that under conditions of NH4+ sufficiency, and hence glutamine sufficiency, the octameric form of GS represses nit-2 gene expression and thereby achieves ammonium repression.
Mol Gen Genet 1980
PMID:The role fo glutamine synthetase and glutamine metabolism in nitrogen metabolite repression, a regulatory phenomenon in the lower eukaryote Neurospora crassa. 610 28

The presence of multiple molecular forms (MMF) of glutamine synthetase (GS) has been studied in pumpkin plants and in cotyledons of bean plants. Two MMF of GS have been found in pumpkin leaves and in green cotyledons: chloroplast GS and cytosol GS. Cotyledons of etiolated pumpkin seedlings contain only the cytosol GS. Illumination of etiolated pumpkin seedlings with white light results in the appearance, within one minute, of the second molecular form, the chloroplast GS, which appears to be due to activation rather than de novo synthesis of the enzyme. Cotyledons of resting seeds of horse bean, pea, soybean and lupine contain only one form of GS. The second form, chloroplast GS, appears after germination in the light, but only in those cotyledons of soybean and lupine that can become green.
Mol Cell Biochem 1981 Oct 30
PMID:Effect of light on the formation of multiple molecular forms of glutamine synthetase in plants. 611 28

A number of mutants have been isolated which affect regulation of the nitrogen fixation (nif) gene cluster in Klebsiella pneumoniae and all of which are linked to glnA, the structural gene for glutamine synthetase (G.S.). These mutants were classified on the basis of their G.S. and nitrogenase activities in conditions of nitrogen limitation and excess. The plasmid R68.45 was then used to generate a number of R-primes carrying the glnA region of the K. pneumoniae chromosome. One of these R-primes (pGE10) was subsequently used in complementation analysis and by isolation of transposon-induced insertion mutations in pGE10 we have demonstrated the existence of a gene, glnG, closely linked to glnA. Mutations in glnG have a similar phenotype to glnG mutants described in Escherichia coli (Pahel and Tyler 1979) and Salmonella typhimurium (Kustu et al. 1979) in that substantially reduce G.S. activity but are not glutamine auxotrophs. GlnG mutants have very low nitrogenase activity indicating that the glnG product may be involved regulation of the nif gene cluster in K. pneumoniae.
Mol Gen Genet 1981
PMID:Complementation analysis of glnA-linked mutations which affect nitrogen fixation in Klebsiella pneumoniae. 612 Apr 41

The glnA, ntrB and ntrC genes of Klebsiella pneumoniae have been cloned, on a 12 kb HindIII fragment, into the plasmid pACYC184. In a coupled in vitro transcription/translation system the resultant plasmid, pGE100, directed synthesis of five polypeptides (molecular weights 73, 53, 51, 39, 36 kd) from the cloned fragment. A number of plasmids were derived from pGE100 and studied by complementation analysis and in vitro transcription/translation in order to locate particular genes and identify their products. On the basis of the results presented here, together with previous genetic and physical characterisation of the glnA gene and its product in other enteric bacteria, we propose that the 53 kd polypeptide is the glnA gene product (glutamine synthetase monomer). Two polypeptides (36 kd and 51 kd) were synthesised from a 3 kb region previously defined as glnR. In E. coli and S. typhimurium this region comprises two genes ntrB and ntrC with products of 36 kd and 54 kd respectively. This analogy supports the idea that the 36 kd and 51 kd polypeptides are the products of the K. pneumoniae ntrB and ntrC genes respectively. Comparison of these assignments with the physical map of the region indicates a gene order glnA, ntrB, ntrC. Assessment of the Nif phenotype of a glnA-ntrC deletion strain carrying various clones from pGE100 demonstrated that glnA is not required for expression of the nif regulon and that of the three genes cloned, ntrC alone is sufficient for nif expression.
Mol Gen Genet 1982
PMID:Cloning of the glnA, ntrB and ntrC genes of Klebsiella pneumoniae and studies of their role in regulation of the nitrogen fixation (nif) gene cluster. 612

Multiple molecular forms of glutamine synthetase (GS, EC 6.3.1.2) have been studied in pea seeds of different varieties. The number of GS molecular forms in the seeds proved to be related to their colour. Two GS forms in the green seeds have been found and only one of them in the yellow seeds. Green seeds had chlorophyll content amounted to 0.4% of the total pigment content in the leaves. Chloroplasts, somewhat smaller than those in pea leaves of the same variety, have been isolated from green seeds. The presence of the second GS form in the pea green seeds we relate to the chloroplasts. By electrophoretic mobility both forms of GS from the green seeds are not identical to the chloroplast GS and the cytosol GS of leaves. Thus, we believe pea plant to contain, at least, four GS forms.
Mol Cell Biochem 1982 Aug 20
PMID:Multiple molecular forms of glutamine synthetase in pea seeds. 612 24

The effects of transcription and translation inhibitors on NADP-glutamate dehydrogenase and glutamine synthetase synthesis in nitrogen-starving Ankistrodesmus braunii cells have been studied. Considering the results obtained one can suggest that both enzymes are coded in a chloroplast genome and that during nitrogen starvation specific mRNA's are partly transferred from chloroplast into cytoplasm and can be translated there on 80S ribosomes.
Mol Cell Biochem 1982 Sep 03
PMID:The role of chloroplast and cytoplasm in the NADP-glutamate dehydrogenase and glutamine synthetase synthesis in Ankistrodesmus cells. 612 70


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