Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P51532 (transcriptional activator)
 6,546 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Nitric oxide (NO) reductase is an integral membrane component of the anaerobic respiratory chain of Pseudomonas stutzeri that transforms nitrate to dinitrogen (denitrification). The enzyme catalyzes the reduction of NO to nitrous oxide. The structural genes for the NO reductase complex, norC and norB, were sequenced and their organization established by primer extension and Northern blot analysis. The norCB genes encoding the cytochrome c and cytochrome b subunits of the enzyme are contiguous and transcribed as a single 2.0-kb transcript. The promoter region has a canonical recognition motif for the transcriptional activator protein Fnr, centered at -40.5 nucleotides from the initiation site of transcription. No similarity of the derived gene products to known cytochromes of b- or c-type was found in a data bank search. Post-translational processing of the two subunits was limited to the removal of the terminal methionine to leave an N-terminal serine in either subunit. The mature cytochrome c subunit (16508Da, 145 residues) is predicted to be a bitopic protein with a single membrane anchor. The mature cytochrome b subunit (53006Da, 473 residues) is a putatively polytopic, strongly hydrophobic membrane-bound protein with 12 potential transmembrane segments. Several histidine and proline residues were identified with potentially structural and/or functional importance. Mutational inactivation of NO reductase by deletion of norB or the norCB genes affected strongly the in vivo activity of respiratory nitrite reductase (cytochrome cd1), but to a much lesser extent the expression level of this enzyme. In turn, mutational inactivation of the structural gene for cytochrome cd1, nirS, or loss of in vivo nitrite reduction by mutation of the nirT gene, encoding a presumed tetraheme cytochrome, lowered the expression level of NO reductase to 5-20%, but hardly its catalytic activity. The cellular concentration of NO reductase increased again on restoration of nitrite reduction in the nirS::Tn5 mutant MK202 by complementation with nirS or with the heterologous nirK gene, encoding the Cu-containing nitrite reductase from Pseudomonas aureofaciens. Thus, NO may be required as an inducer for its own reductase. Our results show that the nitrite-reducing system and the NO-reducing system are not operating independently from each other but are interlaced by activity modulation and regulation of enzyme synthesis.
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PMID:Nitric oxide reductase from Pseudomonas stutzeri. Primary structure and gene organization of a novel bacterial cytochrome bc complex. 750 88

A genetic response of Escherichia coli to nitric oxide or to superoxide-generating agents such as paraquat is controlled by the soxRS locus. The intracellular redox signals generated by these agents are sensed by the SoxR protein which, when activated, functions as a potent activator of soxS transcription. The resulting increased level of SoxS protein then activates approximately 10 genes that constitute the soxRS regulon. Although the SoxS protein is homologous to the COOH-terminal region of the AraC family of regulatory proteins, the mechanism by which SoxS protein activates the soxRS regulon promoters is unknown. We identified in extracts of cells expressing high levels of SoxS protein a DNA binding activity specific for fragments containing soxRS-regulated promoters. This binding activity was purified to physical homogeneity and proved to be the SoxS protein, as confirmed by NH2-terminal amino acid sequencing. The purified SoxS protein bound specifically to the promoters of the micF, zwf, nfo, and sodA genes. Multiple DNA-protein complexes were formed by SoxS in a concentration-dependent fashion with each of these promoters. This binding of SoxS protein also facilitated the subsequent binding of E. coli RNA polymerase to both the micF and the nfo promoters. The binding sites of SoxS in the zwf and micF promoters were identified by DNase I footprinting, which revealed an extended protected region immediately upstream of the respective -35 sites. These results indicate that the small SoxS protein (M(r) of only 12,900) is a direct transcriptional activator of the oxidative stress genes of the soxRS regulon, although the possible involvement of other proteins in transcription activation by SoxS has not been ruled out.
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PMID:SoxS, an activator of superoxide stress genes in Escherichia coli. Purification and interaction with DNA. 803 83

Inflammatory cytokines may participate in the destruction of pancreatic islets during the pathogenesis of insulin-dependent diabetes mellitus, and the cytokine interleukin-1 (IL-1) strongly inhibits insulin secretion from rat pancreatic islets by a process which involves induction of expression of the inducible isoform of nitric oxide synthase and the overproduction of nitric oxide. The signaling events between IL-1 receptor occupancy and induction of nitric oxide synthase in rat islets involve activation of the transcriptional activator NFkappa B. Because sphingomyelin hydrolysis has been implicated as a signaling process both in NFkappa B activation and in IL-1 action in some cells, we have examined the potential involvement of sphingomyelin hydrolysis in the induction of islet nitric oxide overproduction by IL-1. Rat islet sphingomyelin pools were radiolabeled with [3H]choline, and sphingomyelin was then isolated by normal phase HPLC. Electrospray ionization-mass spectrometric analysis revealed islet sphingomyelin consists of at least 4 distinct molecular species, and the most abundant of them contained sphingosine as the long chain base and a residue of palmitic acid as the fatty acid substituent. Molecular species containing residues of stearic acid and arachidic acid were also observed. Neither interleukin-1 nor tumor necrosis factor-alpha was found to induce hydrolysis of islet sphingomyelin species, and neither an exogenous, cell-permeant ceramide species (N-acetyl-D-sphingosine) nor exogenous sphingomyelinase mimicked or potentiated the effect of IL-1 to increase rat islet nitric oxide generation, as reflected by nitrite production. Similar findings were obtained with RINm5F insulinoma cells and with mouse pancreatic islets. These findings provide the first information on the molecular species of sphingomyelin in pancreatic islets and suggest that sphingomyelin hydrolysis is not involved in the signaling pathway whereby IL-1 induces the overproduction of nitric oxide by pancreatic islets.
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PMID:Characterization of the sphingomyelin content of isolated pancreatic islets. Evaluation of the role of sphingomyelin hydrolysis in the action of interleukin-1 to induce islet overproduction of nitric oxide. 860 64

SoxR is a transcriptional activator that senses superoxide and nitric oxide stress in Escherichia coli. The active protein isolated from E. coli contains a pair of [2Fe-2S] clusters per SoxR dimer. We previously demonstrated that the iron-free protein (apo-SoxR), isolated during purification in thiol-containing buffers, binds soxS promoter DNA with an affinity equal to that of the metalloprotein (Fe-SoxR), but lacks significant ability to activate transcription in vitro. Here we demonstrate the reversibility of this process: the full transcriptional activity of SoxR can be restored by in vitro assembly of iron-sulfur clusters into the apoprotein. Two methods were used to synthesize the metallocenters of SoxR: (i) nonenzymatic, in which apo-SoxR, incubated in the presence of iron, inorganic sulfide, and a reducing agent, regained full transcriptional activity in 5-6 h; (ii) enzymatic, in which NifS protein of Azotobacter vinelandii regenerated active Fe-SoxR in as little as 2 min. Analysis by electron paramagnetic resonance spectroscopy indicated that binuclear [2Fe-2S] clusters were restored by both the enzymatic and nonenzymatic reconstitutions. A mutant SoxR protein missing one of its four cysteine residues failed to undergo either transcriptional activation or the formation of [2Fe-2S] centers, even in the presence of NifS. Thus, only the presence of an iron-sulfur center is required to restore transcriptional activity to apo-SoxR. Moreover, the catalytic generation of [2Fe-2S] centers extends the known specificity of this enzyme beyond that already shown for [4Fe-4S] centers. Catalytic generation of [2Fe-2S]-containing SoxR could allow for rapid activation of this transcription factor in vivo.
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PMID:Activation of SoxR-dependent transcription in vitro by noncatalytic or NifS-mediated assembly of [2Fe-2S] clusters into apo-SoxR. 863 39

During denitrification, freely diffusible nitric oxide (NO) is generated for use as a terminal electron acceptor. NO is produced by nitrite reductase (Nir) and reduced to nitrous oxide by nitric oxide reductase (Nor). Using Nir and Nor-deficient mutants of Rhodobacter sphaeroides 2.4.3, we have shown that the endogenous production of NO or the addition of exogenous NO induces transcription of certain genes encoding Nir and Nor. A Nor-deficient strain was found to be capable of expressing wild type levels of nirK-lacZ and norB-lacZ fusions in medium unamended with nitrogen oxides. When this experiment is performed in the presence of hemoglobin, fusion expression is eliminated. NO and the NO-generator, sodium nitroprusside, can induce expression of both fusions in a strain lacking Nir and the consequent ability to produce NO. Sodium nitroprusside cannot induce expression of nirK-lacZ in a strain lacking the transcriptional activator NnrR (nitrite and nitric oxide reductase regulator). Addition of the cyclic nucleotides cAMP and 8-bromoguanosine-cGMP does not result in expression of either fusion. These results demonstrate that denitrifying bacteria produce NO as a signal molecule to activate expression of the genes encoding proteins required for NO metabolism.
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PMID:Requirement of nitric oxide for induction of genes whose products are involved in nitric oxide metabolism in Rhodobacter sphaeroides 2.4.3. 879 93

Nitrite reductase catalyzes the reduction of nitrite to nitric oxide, the first step in denitrification to produce a gaseous product. We have cloned the gene nirK, which encodes the copper-type nitrite reductase from a denitrifying variant of Rhodobacter sphaeroides, strain 2.4.3. The deduced open reading frame has significant identity with other copper-type nitrite reductases. Analysis of the promoter region shows that transcription initiates 31 bases upstream of the translation start codon. The transcription initiation site is 43.5 bases downstream of a putative binding site for a transcriptional activator. Maximal expression of a nirK-lacZ construct in 2.4.3 requires both a low level of oxygen and the presence of a nitrogen oxide. nirK-lacZ expression was severely impaired in a nitrite reductase-deficient strain of 2.4.3. This suggests that nirK expression is dependent on nitrite reduction. The inability of microaerobically grown nitrite reductase-deficient cells to induce nirK-lacZ expression above basal levels in medium unamended with nitrate demonstrates that changes in oxygen concentrations are not sufficient to modulate nirK expression.
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PMID:Characterization and regulation of the gene encoding nitrite reductase in Rhodobacter sphaeroides 2.4.3. 902 88

Several prokaryotic regulatory proteins that respond to changes in oxygen tension or the presence of oxidative agents have now been identified. The Fnr protein governs the expression of numerous genes during anaerobic growth, both as a transcriptional activator and as a repressor. OxyR protein responds to cellular exposure to H2O2 to stimulate transcription of several defense proteins. SoxR protein is triggered by superoxide or nitric oxide to activate a multigene regulon for antioxidant defense and antibiotic resistance. Each of these proteins has been purified and characterized for DNA binding and transcriptional activity in vitro. Fnr, OxyR, and SoxR all seem to respond directly to redox signals generated in the cell, and their in vitro properties support this view: Fnr has an oxygen-sensitive [4Fe-4S] center essential for DNA binding; OxyR may be activated via oxidation of a key cysteine residue; and SoxR activation depends on redox-sensitive [2Fe-2S] centers. Basic methods for genetic and biochemical analysis in these systems are presented, with emphasis on detailed methods for SoxR that illustrate general approaches for all the systems.
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PMID:Study of redox-regulated transcription factors in prokaryotes. 907 70

By using the 'lacZ gene, the activities of the nirI, nirS, and norC promoters were assayed in the wild type and in NNR-deficient mutants of Paracoccus denitrificans grown under various growth conditions. In addition, induction profiles of the three promoters in response to the presence of various nitrogenous oxides were determined. Transcription from the three promoters required the absence of oxygen and the presence both of the transcriptional activator NNR and of nitric oxide. The activity of the nnr promoter itself was halved after the cells had been switched from aerobic respiration to denitrification. This response was apparently not a result of autoregulation or of regulation by FnrP, since the nnr promoter was as active in the wild-type strain as it was in NNR- or FnrP-deficient mutants.
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PMID:Nitric oxide is a signal for NNR-mediated transcription activation in Paracoccus denitrificans. 1038 87

The induction kinetics of the mRNA of interferon regulatory factor 1 (IRF-1), inducible nitric oxide synthase (iNOS), and proinflammatory cytokines in respiratory syncytial virus (RSV)-infected human type 2 alveolar epithelial cells (A549 cells) were analyzed semiquantitatively by RT-PCR. RSV enhanced IRF-1 and iNOS mRNA expression as early as 4 h after RSV infection and this enhancement lasted several hours. No IFN-gamma gene expression was observed during the whole course of the infection. Expression of IFN-beta, IL-1beta, and TNF-alpha genes was observed slightly at 4 h and became marked 7 h after infection. Addition of neutralizing antibodies to these cytokines to the culture had no effect on the induction of iNOS mRNA. The iNOS transcriptional activity in RSV-infected cells was significantly enhanced by an exogenous cytokine mixture (IL-1beta, TNF-alpha, and IFN-gamma). An apparent nitric oxide (NO) production was identified only when cytokines were added together with RSV infection. A significant increase of iNOS gene expression was observed in nasopharyngeal exudate cells obtained from infants during the acute phase of RSV bronchiolitis. These observations suggest that RSV infection of human respiratory epithelial cells induces the iNOS gene both in vitro and in vivo; this induction may occur rather promptly and involves transcriptional activator IRF-1 induced by the RSV infection itself. The iNOS gene, which is initially induced by RSV infection, may be further enhanced in a paracrine fashion by proinflammatory cytokines released by infection-activated inflammatory cells.
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PMID:Respiratory syncytial virus infection of human respiratory epithelial cells enhances inducible nitric oxide synthase gene expression. 1041 Sep 96

Nitric oxide (NO) was found to inhibit the copper-dependent induction of the yeast CUP1 gene. This effect is attributable to an inhibition of the copper-responsive CUP1 transcriptional activator Ace1. A mechanism is proposed whereby the metal binding thiols of Ace1 are chemically modified via NO- and O(2)-dependent chemistry, thereby diminishing the ability of Ace1 to bind and respond to copper. Moreover, it is proposed that demetallated Ace1 is proteolytically degraded in the cell, resulting in a prolonged inhibition of copper-dependent CUP1 induction. These findings indicate that NO may serve as a disrupter of yeast copper metabolism. More importantly, considering the similarity of Ace1 to other mammalian metal-binding proteins, this work lends support to the hypothesis that NO may regulate/disrupt metal homeostasis under both normal physiological and pathophysiological circumstances.
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PMID:The interaction of nitric oxide (NO) with the yeast transcription factor Ace1: A model system for NO-protein thiol interactions with implications to metal metabolism. 1069 79


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