Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0031511 (pheochromocytoma)
 14,622 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The glnA gene of the cyanobacterium Agmenellum quadruplicatum PR-6 (Synechococcus sp. strain PCC 7002) was isolated by complementing an Escherichia coli strain auxotrophic for glutamine (YMC11) with a PR-6 cosmid library. PR-6 glnA is a single-copy gene that encodes a deduced amino acid sequence that is highly homologous to the deduced glnA amino acid sequences reported for other bacteria. No homology was found between the PR-6 glnA flanking sequences and the ntrB, ntrC, or glnB genes of other bacteria. Northern (RNA) and primer extension analyses of PR-6 RNA revealed one predominant and several minor glnA transcripts of about 1.5 to 1.7 kb. The steady-state amounts of these transcripts increased three- to fivefold when the cells were starved for nitrogen. However, we found that mutant PR-6 cells lacking glnA were still able to use nitrate or ammonium as a sole nitrogen source. Although no RNA homologous to an internal fragment of the glnA gene could be detected in the mutant cells, they retained about 60% of wild-type glutamine biosynthetic activity. The mutant cells were more sensitive than the wild-type cells to methionine sulfoximine, a transition state analog of glutamate, a result that might indicate the presence of an additional glutamine synthetase; however, cell extracts of wild-type PR-6 cells and those lacking glnA were both able to use carbamyl phosphate instead of ammonium as a nitrogen donor for the synthesis of glutamine, a result that indicates the use of carbamyl phosphate synthetase to assimilate ammonium and produce glutamine.
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PMID:The glnA gene of the cyanobacterium Agmenellum quadruplicatum PR-6 is nonessential for ammonium assimilation. 767 91

The upstream noncoding region of the Synechococcus sp. strain PCC 7942 (hereafter referred to as Synechococcus 7942) glnA gene was fused to the cat gene in order to study the expression of glnA both in Synechococcus 7942 and in Escherichia coli. The lack of cat expression in E. coli indicated that the glnA promoter was not recognized by E. coli RNA polymerase. The fused construct was integrated into the Synechococcus 7942 chromosome at a neutral site. Expression of the cat reporter gene was regulated under various nitrogen conditions in a way similar to that of the glnA gene. A deletion introduced at the binding site of the NtcA regulatory protein abolished derepression of the glnA promoter during growth in nitrate and under nitrogen starvation. Deletion of the sequence between the transcription and translation start sites of glnA prevented the repression observed during growth in ammonium. These results indicate that the glnA promoter is subject to complex regulation that involves sequences upstream and downstream from the transcription start site.
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PMID:Characterization of cis elements that regulate the expression of glnA in Synechococcus sp. strain PCC 7942. 772 15

A stable DNA/protein complex having an apparent molecular mass of approximately 150 kDa was purified from nitrate-limited cultures of the cyanobacterium Synechococcus sp. strain PCC 7942. Amino-terminal peptide sequencing indicated that the polypeptide was structurally similar to the Dps protein of Escherichia coli; Dps is also known as the product of the starvation- and stationary-phase-inducible gene, pexB. The 150-kDa complex dissociated into a 22-kDa protein monomer after boiling in 2% SDS. The 150-kDa complex preparation had approximately a 10% nucleic acid content and upon dissociation released DNA fragments that were sensitive to S1 nuclease digestion. Immunoblot data indicated that the complex accumulates during stationary phase and during nitrogen, sulfur, and phosphorus limitation. DNA-binding assays indicated that the protein nonspecifically binds both linear and supercoiled DNA. Circular dichroism spectroscopy revealed that the Synechococcus sp. Dps-like protein contains extensive regions of alpha-helical secondary structure. We propose that the 150-kDa complex represents a hexameric aggregate of the Dps-like protein complexed with single-stranded DNA and serves to bind a portion of the chromosomal DNA under nutrient-limited conditions.
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PMID:Purification and characterization of a Synechococcus sp. strain PCC 7942 polypeptide structurally similar to the stress-induced Dps/PexB protein of Escherichia coli. 779 1

The Anabaena sp. strain PCC 7120 ntcA (bifA) gene encodes a sequence-specific DNA-binding protein, NtcA (BifA, VF1) that interacts with the upstream region of several genes, including glnA, xisA, rbcL, and nifH. We have constructed a ntcA null mutant by interrupting the gene with an omega Spr-Smr cassette. The ntcA mutant was not able to grow with nitrate or atmospheric dinitrogen as the sole nitrogen source but could be grown on medium containing ammonium. The ntcA mutant was unable to form heterocysts and did not rearrange the nifD or fdxN elements after induction on a medium lacking combined nitrogen. Northern (RNA) analysis of ntcA in the wild-type strain during nitrogen stepdown showed a peak of ntcA message at an early stage (12 h) of heterocyst induction. Complementation of the ntcA mutant with a DNA fragment containing the ntcA gene and 251 bp of upstream sequence on a shuttle vector restored a wild-type phenotype; however, a similar construction containing 87 bp of upstream sequence only partially restored the phenotype. Northern analysis of RNA samples isolated from ammonium-grown cultures of the ntcA mutant showed reduced amounts of glnA message and the absence of a 1.7-kb transcript. In the wild type, the 1.7-kb transcript represents the majority of glnA transcripts after nitrogen stepdown. The ntcA mutant showed a normal pattern of rbcLS messages under these growth conditions.
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PMID:Anabaena sp. strain PCC 7120 ntcA gene required for growth on nitrate and heterocyst development. 791 26

The existence in the unicellular cyanobacterium Synechocystis sp. strain PCC 6803 of two genes (glnA and glnN) coding for glutamine synthetase (GS) has been recently reported (J.C. Reyes and F.J. Florencio, J. Bacteriol. 176:1260-1267, 1994). In the current work, the regulation of the nitrate assimilation system was studied with a glnA-disrupted Synechocystis mutant (strain SJCR3) in which the only GS activity is that corresponding to the glnN product. This mutant was unable to grow in ammonium-containing medium because of its very low levels of GS activity. In the SJCR3 strain, nitrate and nitrite reductases were not repressed by ammonium, and short-term ammonium-promoted inhibition of nitrate uptake was impaired. In Synechocystis sp. strain PCC 6803, nitrate seems to act as a true inducer of its assimilation system, in a way similar to that proposed for the dinitrogen-fixing cyanobacteria. A spontaneous derivative strain from SJCR3 (SJCR3.1), was able to grow in ammonium-containing medium and exhibited a fourfold-higher level of GS activity than but the same amount of glnN transcript as its parental strain (SJCR3). Taken together, these finding suggest that SJCR3.1 is a mutant affected in the posttranscriptional regulation of the GS encoded by glnN. This strain recovered regulation by ammonium of nitrate assimilation. SJCR3 cells were completely depleted of intracellular glutamine shortly after addition of ammonium to cells growing with nitrate, while SJCR3.1 cells maintained glutamine levels similar to that reached in the wild-type Synechocystis sp. strain PCC 6803. Our results indicate that metabolic signals that control the nitrate assimilation system in Synechocystis sp. strain PCC 6803 require ammonium metabolism through GS.
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PMID:A mutant lacking the glutamine synthetase gene (glnA) is impaired in the regulation of the nitrate assimilation system in the cyanobacterium Synechocystis sp. strain PCC 6803. 800 75

Long-chain acylcarnitines (12-18 carbon fatty acid esters) dramatically enhance the absorption of hydrophilic drugs across intestinal mucosa without altering the morphology of the epithelium. The mechanism underlying these effects was studied using the colon carcinoma cell line Caco-2. Caco-2 monolayers treated with 0.2 mM palmitoylcarnitine (PCC) show dramatic increases in the transport of hydrophilic markers. This enhanced transport coincides with a rapid drop in transepithelial electrical resistance (TER). The drop in TER is initiated within the first minute after PCC addition and continues for approximately 20 min to a 70 to 85% drop of the initial TER values. This effect is reversible after removing the PCC and does not appear to involve lysis of the apical membrane. Instead PCC's effect appears to be due to loosening of tight junctions as indicated by the accumulation of fluorescent dextrans and the electron dense marker lanthanum nitrate in paracellular spaces. Moreover transmission electron microscopy and freeze fracture electron microscopy indicate that PCC produces significant structural alterations to tight junctions. In contrast to many other tight junction disrupting agents, PCC effects appear to be Ca(++)-independent and PCC does not induce significant disruption of actin filament distribution in Caco-2 cells.
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PMID:In vitro and in vivo analysis of the mechanism of absorption enhancement by palmitoylcarnitine. 818 50

Biochemical properties of the ATPase from the plasma membrane of the cyanobacteria Synechococcus PCC 6311 and PCC 7942 were examined. ATPase activity associated with purified plasma membrane vesicles was strongly inhibited by 100 microM vanadate (87%), 100 microM diethylstilbestrol (70%) and 100 mM fluoride ions (83%). No inhibition was observed in the presence of dicyclohexylcarbodiimide, nitrate, azide, or molybdate. A 50% activation was observed in the presence of 50 mM KCl but none was observed in the presence of NaCl or NH4Cl. This ATPase was able to form a pH gradient, the amplitude of which was decreased by the presence of 100 microM vanadate. On Western blot of the plasmalemma proteins, no labeling was observed with a monoclonal antibody against the beta subunit of the F0-F1 ATPase, although staining was observed with the 55-kDa subunit of the thylakoid membrane ATPase. After phosphorylation of plasmalemma vesicles, by [gamma-32P]ATP, the autoradiograms of the electrophoreses, performed under acid conditions, exhibited labeling of a 110-kDa protein. The results indicated that the Synechococcus plasma membrane ATPase can be classified as a H+ translocating P-type ATPase and compared to the plant plasmalemma ATPase.
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PMID:Characterization of the plasmalemma ATPase from the cyanobacteria Synechococcus PCC 6311 and PCC 7942. 821 12

The nucleotide sequence of the structural gene of nitrate reductase (n ar beta) has been determined from the filamentous, non-heterocystous cyanobacterium Oscillatoria chalybea. The nar beta gene encodes a protein of 737 amino acid residues, which shows 61% identity to nitrate reductase of the unicellular cyanobacterium Synechococcus sp. PCC 7942 and only weak homologies to different bacterial molybdoenzymes, such as nitrate reductases or formate dehydrogenases.
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PMID:Nucleotide sequence of the nar beta gene encoding assimilatory nitrate reductase from the cyanobacterium Oscillatoria chalybea. 860 43

The narB gene from the cyanobacterium Synechococcus sp. PCC 7942 was cloned downstream from the LacI-regulated promoter Ptrc in the Escherichia coli vector pTrc99A, rendering plasmid pCSLM1. Addition of isopropyl-beta-D-thiogalactoside to E. coli (pCSLM1) resulted in the parallel expression of a 76 kDa polypeptide and a nitrate reductase activity with properties identical to those known for nitrate reductase isolated from Synechococcus cells. As is the case for nitrate reductase from Synechococcus cells, either reduced methyl viologen or reduced ferredoxin could be used as an electron donor for the reduction of nitrate catalyzed by E. coli (pCSLM1) extracts. This data shows that narB is a cyanobacterial structural gene for nitrate reductase.
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PMID:A cyanobacterial narB gene encodes a ferredoxin-dependent nitrate reductase. 862 15

A mutant (M45) of the cyanobacterium Synechococcus sp. strain PCC 7942, which is defective in active transport of nitrate, was used for the studies of the nitrogen regulation of the genes involved in nitrate and CO2 assimilation. In a medium containing 30 mM nitrate as the nitrogen source, M45 grew under constant stress of nitrogen deficiency and accumulated a five-times-larger amount of the transcript of nirA, the gene for nitrite reductase, compared with nitrate-grown wild-type cells. By contrast, the level of the transcript of rbcL, the gene for the large subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase, was 40% of the wild-type level. Addition of ammonium to the culture of M45 abolished the accumulation of the nirA transcript and stimulated the accumulation of the rbcL transcript, showing that ammonium repressed and activated the transcription of nirA and rbcL, respectively. Glutamine, the initial product of ammonium fixation, also showed negative and positive effects on nirA and rbcL, respectively. One of the metabolites of glutamine, carbamoylphosphate, and its decomposition product, cyanate, were found to repress nirA and also to markedly activate rbcL. Cyanate negatively regulated another ammonium-repressible gene, glnA, but had no effect on the psbAI and rps1 genes. The effects of cyanate were not ascribable to the ammonium and CO, resulting from its decomposition. These findings suggested that cyanate may act as a regulator of the ammonium-responsive genes involved in carbon and nitrogen assimilation in the cyanobacterium.
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PMID:Regulation by cyanate of the genes involved in carbon and nitrogen assimilation in the cyanobacterium Synechococcus sp. strain PCC 7942. 862 39


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