Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.7.6 (RNA polymerase)
 34,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Rifampin-resistant (Rifr) mutants were isolated spontaneously from Bacillus subtilis strain 168. A fraction of the mutants did not grow on a minimal medium. A high concentration of one of the L-amino acids (glutamic acid, glutamine, arginine, proline, aspartic acid, or asparagine) was required to restore their growth on the medium. Further analysis of one of the mutants (strain RF 161) suggested that the mutant is unable to use ammonia as a nitrogen source and requires amino acids instead. Activity of glutamate synthase was not detected in the crude extract of the mutant. The Rifr mutation was closely located to cysA and the drug resistance was cotransformed with the property of amino acid requirement at 100% frequency. All revertants to prototrophy tested showed the rifampin-sensitive (Rifs) property. The activity of the DNA-dependent RNA polymerase of the mutant was resistant to rifampin. It is concluded that some alteration of RNA polymerase may cause absence of the activity of an enzyme involved in the nitrogen metabolism.
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PMID:Pleiotropic effect of a rifampin-resistant mutation in Bacillus subtilis. 9 17

Spore formation of 15 rifampin-resistant (Rifr) mutants of Bacillus subtilis strain 168 was examined. As a pleiotropic effect of a Rifr mutation, glutamate synthase activity was lost in these mutants. Twelve of the 15 mutants examined formed as many spores as the parent, but the remaining 3 formed significantly fewer (1%) spores. One of the latter mutants characterized further (RF301) was blocked in its sporulation process at stage 0. Thus, it was concluded that a certain modification of ribonucleic acid polymerase may affect specifically the gene expression of glutamate synthase and also the sporulation process at the initial stage.
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PMID:Ribonucleic acid polymerase mutation affecting glutamate synthase activity in and sporulation of Bacillus subtilis. 11 Jul 92

An Azospirillum brasilense mutant (N12) pleiotropically defective in the assimilation of nitrogenous compounds (Asm-) was isolated and found lacking in the glutamate synthase (GOGAT-). The glt (GOGAT) locus of A. brasilense was identified by isolating a broad-host-range pLAFR1 cosmid clone from a gene library of the bacterium that rectified Asm- and GOGAT- defects (full recovery of activities of the nitrogenase, the assimilatory nitrate and nitrite reductases, and the glutamate synthase). A 7.5-kb EcoRI fragment of the cosmid clone that also complemented N12 was partially sequenced to identify the open reading frame for the alpha-subunit of GOGAT. The amino acid sequences deduced from the partial nucleotide sequences of the glt locus of A. brasilense showed considerable homology with that of the alpha-subunit of GOGAT coded by the gltB gene of Escherichia coli. The genetic lesion of N12 was found within the gltB gene of A. brasilense. The gltB promoter of A. brasilense showed the presence of a consensus sigma-70-like recognition site (as in E. coli) in addition to potential NtrA-RNA polymerase, IHF, and NifA binding sites.
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PMID:Isolation of a glutamate synthase (GOGAT)-negative, pleiotropically N utilization-defective mutant of Azospirillum brasilense: cloning and partial characterization of GOGAT structural gene. 790 33

Cultured astrocytes derived from neonatal rat brain exhibited high affinity, Na+-dependent, paroxetine and fluoxetine sensitive [3H]5-HT uptake. Reverse transcriptase-PCR demonstrated that astrocytes in culture expressed messenger RNA for the cloned serotonin transporter protein which has been characterised as the neuronal serotonin transporter. Although the serotonin transporter in cultured astrocytes displayed a Km value approximately 10 times greater than found in adult brain synaptosomes, these observations indicated that astrocytes in vitro may express the same serotonin transporter as neurons. Reverse transcriptase-PCR demonstrated the presence of serotonin transporter mRNA in the adult rat cerebral cortex, suggesting that astrocytes in vivo may express low levels of this mRNA. To investigate whether astrocytes in the adult CNS express functional serotonin transporters, glial plasmalemmal vesicles were prepared from cerebral cortex, representing a subcellular fraction composed primarily of vesicles derived from astrocytes. These vesicles were characterised by [3H]-glutamate and [3H]-dopamine uptake and by immunoblot analysis, using glial and synaptic markers: glutamate synthase, SNAP-25 and synaptobrevin. [3H]5-HT was taken up into glial plasmalemmal vesicles in a high affinity (Km approximately 40 nM), Na+ dependent, paroxetine-sensitive manner. The [3H]5-HT uptake capacity (Vmax) in these vesicles was approximately one quarter of that observed in synaptosomes. These data indicate that astrocytes in culture and in vivo are capable of 5-HT uptake via the previously characterised 'neuronal' serotonin transporter.
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PMID:Serotonin transporters in adult rat brain astrocytes revealed by [3H]5-HT uptake into glial plasmalemmal vesicles. 969 37

The leucine-responsive regulatory protein (Lrp) binds to three sites centered 252, 216, and 152 bp upstream of the transcription start site of the Escherichia coli glutamate synthase operon (gltBDF) and activates transcription. Activators of sigma(70)-dependent promoters usually bind closer to the -35 hexamer of the core promoter sequence. To study the mechanism by which Lrp-dependent activation occurs over this relatively large distance, the gltBDF upstream region was sequentially replaced with corresponding portions from the well-characterized sigma(70)-dependent promoter lacZYAp. The glt-lac promoter hybrids were placed upstream of lacZ, allowing transcriptional activity to be monitored via beta-galactosidase assays. Even replacing all gltBDF sequences downstream of and including the -35 hexamer did not eliminate Lrp-dependent activation of transcription. When a 91-bp region between the -35 hexamer and the proximal Lrp binding site (-48 to -128) was replaced with heterologous DNA of the same length, transcription was reduced nearly 40-fold. Based on the presence of a consensus binding sequence, this region seemed likely to be a binding site for integration host factor (IHF). Experiments to study the effects of a himD mutant on expression of a gltB::lacZ transcriptional fusion, gel mobility shift analyses, and DNA footprinting assays were used to confirm the direct participation of IHF in gltBDF promoter regulation. Based on these results, we suggest that IHF plays a crucial architectural role, bringing the distant Lrp complex in close proximity to the promoter-bound RNA polymerase.
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PMID:Activation from a distance: roles of Lrp and integration host factor in transcriptional activation of gltBDF. 1139 54

In Bacillus subilis, glutamate synthase, a major enzyme of nitrogen metabolism, is encoded by the gltAB operon. Significant expression of this operon requires the activity of GltC, a LysR-family protein, encoded by the divergently transcribed gene. We purified a soluble, active form of GltC and found that it requires alpha-ketoglutarate, a substrate of glutamate synthase, to fully activate gltA transcription in vitro, and that its activity is inhibited by glutamate, the product of glutamate synthase. GltC regulated gltAB transcription through binding to three dyad-symmetry elements, Box I, Box II and Box III, located in the intergenic region of gltC and gltA. Free GltC bound almost exclusively to Box I and activated gltAB transcription only marginally. Glutamate-bound GltC bound to Box I and Box III, and repressed gltAB transcription. In the presence of alpha-ketoglutarate, GltC bound to Box I and Box II, stabilized binding of RNA polymerase to the gltA promoter, and activated gltAB transcription. The binding of GltC to Box II, which partially overlaps the -35 region of the gltA promoter, seems to be essential for activation of the gltAB operon. Due to the high concentration of glutamate in B. subtilis cells grown under most conditions, alterations of the concentration of alpha-ketoglutarate seem to be crucial for modulation of GltC activity and gltAB expression.
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PMID:Molecular mechanism of the regulation of Bacillus subtilis gltAB expression by GltC. 1713 17