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)

The cloned Pseudomonas aeruginosa fur (ferric uptake regulator) gene was overexpressed in P. aeruginosa by using a T7 expression system, and the Fur protein (PA-Fur) was purified by using a combination of ion-exchange chromatography and metal affinity chromatography. The DNA binding activity of the PA-Fur protein was confirmed by gel mobility shift assays and DNase I footprints of the synthetic DNA fragment GATAAT GATAATCATTATC, representing a perfect "Fur box". In addition, it was shown that PA-Fur is capable of binding to promoter and operator determinants of the tightly iron-regulated Escherichia coli fepA-fes enterobactin gene system. The activity of PA-Fur on the promoters of iron-regulated genes involved in the production of two siderophores, pyochelin and pyoverdin, and in the expression of exotoxin A was investigated. Data indicating that the promoters of the pchR gene, encoding a transcriptional activator for pyochelin synthesis, and of the pvdS gene, encoding a positive regulator for pyoverdin production, are specifically recognized by Fur-Fe(II) are presented, suggesting that PA-Fur represses expression of pchR and pvdS during growth in an iron-replete environment. However, neither the promoter region of the gene encoding exotoxin A (toxA) nor the promoters of the regAB operon, required for toxA expression, interacted with high concentrations of purified PA-Fur. These data indicate that iron regulation of exotoxin A production involves additional factors which may ultimately be under the control of PA-Fur.
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PMID:Role of the ferric uptake regulator of Pseudomonas aeruginosa in the regulation of siderophores and exotoxin A expression: purification and activity on iron-regulated promoters. 852 28

The lemA gene of Pseudomonas syringae pv. syringae encodes the sensor kinase of a bacterial two-component signal transduction system. Phenotypes that are lemA dependent in P. syringae include lesion formation on bean and production of extracellular protease and the antibiotic syringomycin. Recently, the gacA gene has been identified as encoding the response regulator of the lemA regulon. To identify additional components that interact with LemA, suppressors of a lemA mutation were sought. A locus was identified that, when present in multiple copies, restores extracellular protease production to a lemA insertion mutant of P. syringae pv. syringae. This locus was found to encode the P. syringae homologs of translation initiation factor IF3 and ribosomal proteins L20 and L35 of Escherichia coli and other bacteria. Deletion analysis and data from Western immunoblots with anti-IF3 antiserum suggest that protease restoration does not require IF3. Deletion of both the L35 and L20 genes resulted in loss of protease restoration, whereas disruption of either gene alone increased protease restoration. Our results suggest that overexpression of either L20 or L35 is sufficient for protease restoration. It is unclear how alteration of ribosomal protein expression compensates in this instance for loss of a transcriptional activator, but a regulatory role for L20 and L35 apart from their function in the ribosome may be indicated.
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PMID:Suppression of a sensor kinase-dependent phenotype in Pseudomonas syringae by ribosomal proteins L35 and L20. 862 80

BkdR is the transcriptional activator of the bkd operon of Pseudomonas putida, which encodes branched chain keto acid dehydrogenase. BkdR binds to a large region of DNA between its own structural gene and the first gene of the bkd operon. The object of the present studies was to determine the stoichiometry of binding as part of an effort to understand the action of BkdR in regulation of the bkd operon. [35S]BkdR was prepared and found to be essentially 100% active in the gel shift assay. Only one complex was formed under all the conditions used. The stoichiometry of BkdR binding to its specific substrate DNA was three tetramers per mold substrate DNA. L-valine did not affect the stoichiometry although this ligand was previously shown to affect the DNase I protection pattern. The addition of nonspecific DNA to the incubation mixture also did not affect this stoichiometry.
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PMID:Stoichiometry of BkdR to substrate DNA in Pseudomonas putida. 867 Feb 79

A series of structural analogs of the Pseudomonas aeruginosa autoinducer [PAI, N-3-oxo-dodecanoyl homoserine lactone] were obtained and tested for their ability to act as autoinducers in stimulating the expression of the gene for elastase (lasB) by measuring beta-galactosidase production from a lasB-lacZ gene fusion in the presence of the transcriptional activator LasR. The data suggest that the length of the acyl side chain of the autoinducer molecule is the most critical factor for activity. Replacement of the ring O by S in the homoserine lactone moiety can be tolerated. Tritium-labelled PAI ([3H]PAI) was synthesized and used to demonstrate the association of [3H]PAI with cells overexpressing LasR. The PAI analogs were also tested for their ability to compete with [3H]PAI for binding of LasR. Results from the competition assays suggest that once again the length of the acyl side chain appears to be crucial for antagonist activity. The presence of the 3-oxo moiety also plays a significant role in binding since analogs which lacked this moiety were much less effective in blocking binding of [3H]PAI. All analogs demonstrating competition with PAI in binding to LasR also exhibited the ability to activate lasB expression, suggesting that they are functional analogs of PAI.
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PMID:Functional analysis of the Pseudomonas aeruginosa autoinducer PAI. 883 Jun 97

The importance of accurate demographic information is reflected in the United States Constitution, Article 1, which provides for a decennial census of this country's human population. Bacteria also conduct a census of their population and do so more frequently, more efficiently, and as far we know, with little if any of the political contentiousness caused by human demographers. Many examples have been found of particular bacterial genes, operons, or regulons that are expressed preferentially at high cell densities. Many of these are regulated by proteins related to the LuxR and LuxI proteins of Vibrio fischeri, and by a diffusible pheromone called an autoinducer. LuxR and LuxI and their cognate autoinducer (3-oxohexanoyl homoserine lactone, designated VAI-1) provide an important model to describe the functions of this family of proteins. LuxR is a VAI-1 receptor and a VAI-1-dependent transcriptional activator, and LuxI directs the synthesis of VAI-1. VAI-1 diffuses across the bacterial envelope, and intracellular concentrations of it are therefore strongly increased by nearby VAI-1-producing bacteria. Similar systems regulate pathogenesis factors in Pseudomonas aeruginosa and Erwinia spp., as well as T1 plasmid conjugal transfer in Agrobacterium tumefaciens, and many other genes in numerous genera of gram-negative bacteria. Genetic analyses of these systems have revealed a high degree of functional conservation, while also uncovering features that are unique to each.
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PMID:Census and consensus in bacterial ecosystems: the LuxR-LuxI family of quorum-sensing transcriptional regulators. 890 97

RegA is a transcriptional activator that controls exotoxin A (ETA) production in Pseudomonas aeruginosa. To date, functional assays performed with the purified protein have not clearly defined the molecular mechanism of action of RegA. In this study, we sought to identify important coding regions of regA by analysing the sequences around linker insertion mutations in regA that affected toxA transcription. First, we constructed a strain with the regAB locus deleted from the chromosome, PA103 delta regAB::Gm. toxA transcription was obliterated in strain PA103 delta regAB::Gm, demonstrating that the regAB locus is essential for ETA production. Next, we constructed a series of 6 bp linker insertion mutations distributed throughout regA. These regA linker insertion mutants were sequenced and screened in PA103 delta regAB::Gm for their effects on regulation of ETA production. Six linker insertion mutations occurring between amino acids (aa) 53 and 163 of RegA were isolated that resulted in depression of toxA transcription to varying levels relative to the parental regAB locus. One of these linker insertion mutations (pTR53), resulted in a lack of iron-regulated ETA production and occurred directly upstream from a predicted transmembrane alpha-helix. The other five linker mutations (pTR88, pTR124, pTR132, pTR132-2 and pTR163) occurred within or flanked a region of RegA between aa 87-142 with similarity to the transcriptional activation domains of ToxR, VirG and OmpR. These data suggest the presence of a previously unidentified transcriptional activation domain in RegA between aa 87-142 and implicate the predicted transmembrane alpha-helix in the N-terminus as being involved in sensory transduction.
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PMID:Linker insertion scanning of regA, an activator of exotoxin A production in Pseudomonas aeruginosa. 893 Sep 9

Alginate production in mucoid Pseudomonas aeruginosa isolates from cystic fibrosis patients is under direct control by AlgU, the P. aeruginosa equivalent of the extreme heat shock sigma factor sigma(E) in gram-negative bacteria, and AlgR, a response regulator from the superfamily of two-component signal transduction systems. In this report, we describe the identification of the algZ gene, located immediately upstream of algR, which is involved in the control of alginate production. The predicted product of the algZ gene showed similarity to a subset of sensory components from the superfamily of signal transduction systems but lacked several of the highly conserved motifs typical of histidine protein kinases. Inactivation of algZ in the wild-type standard genetic strain PAO1 did not affect its nonmucoid morphology. However, inactivation of algZ in a mucoid mutant P. aeruginosa strain, which had AlgU freed from control by the anti-sigma factor MucA, resulted in increased alginate production under growth conditions which did not permit expression of mucoidy in the parental algZ+ strain. The observed effects were abrogated when algR was inactivated in the algZ::Tc(r) background. These findings indicate that algZ plays a regulatory role in alginate production, possibly interacting with AlgR, and that it may have negative effects on expression of the mucoid phenotype under the conditions tested. The presented results suggest that elements of negative regulation exist at the levels of both the alternative sigma factor AlgU and the transcriptional activator AlgR which, once relieved from that suppression, cooperate to bring about the expression of the alginate system.
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PMID:Identification of the algZ gene upstream of the response regulator algR and its participation in control of alginate production in Pseudomonas aeruginosa. 898 97

BkdR is the positive transcriptional activator of the inducible bkd operon of Pseudomonas putida. Evidence is accumulating that L-branched-chain amino acids are the inducers of the operon, and the data obtained in this study show that they induce a conformational change in BkdR. Addition of L-branched-chain amino acids increased the susceptibility of BkdR to trypsin with the cleavage between Arg-51 and Gln-52 on the C-terminal side of the DNA-binding domain. L-Valine also caused an increased fluorescence emission intensity and produced significant changes in the circular dichroism spectrum of BkdR. Analytical ultracentrifugation confirmed earlier data obtained from gel filtration that BkdR was a tetramer with a Stokes radius of 32 +/- 3 A and an axial ratio of 2:1.
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PMID:Binding of L-branched-chain amino acids causes a conformational change in BkdR. 898 9

Two regions of the nopaline-type Ti plasmid pTiC58 are important for conjugal transfer of this element to recipient bacteria. These two regions were cloned into two independent replicons to produce a binary transfer system. For one region, oriT/tra, we constructed two derivatives, pFRtra and pDCtra-5. Each contains the oriT site and the two flanking, divergently transcribed tra operons that encode the DNA processing functions associated with the relaxosome. These two plasmids also carry traR, which encodes the transcriptional activator necessary for expression of transfer genes. The two plasmids differ by the amounts of traB sequence or sequence downstream of traG present in the construct. The second replicon, pPLE2, carries the traI/trb region. The traI gene confers production of the Agrobacterium tumefaciens N-acyl homoserine lactone autoinducer, while the remaining genes in the trb operon encode components of the mating bridge. Donors harboring the two plasmids mobilized the transfer of the plasmid carrying the oriT/tra region to an A. tumefaciens recipient at frequencies similar to that at which the intact Ti plasmid transferred. Plasmid pFRtra, which encodes most of traB, was mobilized at a frequency almost 10-fold higher than was pDCtra-5, which lacks most of the gene. A. tumefaciens donors also mobilized pFRtra to Escherichia coli and Pseudomonas fluorescens recipients at frequencies similar to those observed with A. tumefaciens recipients. Rhizobium meliloti harboring the binary system also transferred the oriT/tra component to these recipients. However, E. coli or P. fluorescens donors harboring the binary system did not transfer pFRtra to any of the recipients. Furthermore, while the A. tumefaciens and R. meliloti donors produced high levels of the autoinducer, the P. fluorescens and E. coli donors produced only trace amounts of this signal molecule. These results indicate that the tra system of pTiC58 is fully contained within the characterized tra and trb regions of the Ti plasmid, that conjugation does not require functions encoded by the vir system for maximal activity, and that while the Ti plasmid tra system recognizes diverse gram-negative bacteria as recipients, of the hosts tested, it functions only in members of the family Rhizobiaceae.
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PMID:Ti plasmid conjugation is independent of vir: reconstitution of the tra functions from pTiC58 as a binary system. 902 14

Reinvestigation of the transcriptional start site of the bkd operon of Pseudomonas putida revealed that the transcriptional start site was located 86 nucleotides upstream of the translational start. There was a sigma 70 binding site 10 bp upstream of the transcriptional start site. The dissociation constants for BkdR, the transcriptional activator of the bkd operon, were 3.1 x 10(-7) M in the absence of L-valine and 8.9 x 10(-8) M in the presence of L-valine. Binding of BkdR to substrate DNA in the absence of L-valine imposed a bend angle of 92 degrees in the DNA. In the presence of L-valine, the angle was 76 degrees. BkdR did not bind to either of the two fragments of substrate DNA resulting from digestion with AgeI. Because AgeI attacks between three potential BkdR binding sites, this suggests that binding of BkdR is cooperative. P. putida JS110 and JS112, mutant strains which do not express any of the components of branched-chain keto acid dehydrogenase, were found to contain missense mutations in bkdR resulting in R40Q and T22I changes in the putative helix-turn-helix of BkdR. Addition of glucose to the medium repressed expression of lacZ from a chromosomal bkdR-lacZ fusion, suggesting that catabolite repression of the bkd operon was the result of reduced expression of bkdR. These data are used to present a model for the role of BkdR in transcriptional control of the bkd operon.
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PMID:Transcriptional activation of the bkd operon of Pseudomonas putida by BkdR. 906 46


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