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 Serratia marcescens extracellular nuclease is a secreted protein that is subject to growth phase and SOS control. Regulatory mutants affecting nuclease expression have been isolated that define a new locus, nucC, essential for transcription of the nuclease gene nucA. The cloned nucC gene is able to activate efficient expression from the nucA promoter in Escherichia coli, where it normally is poorly expressed. NucC is very similar to the bacteriophage P2 Ogr protein, a transcriptional activator essential for P2 late gene expression. NucC is able to replace P2 Ogr to support the growth of P2 ogr- mutants in E. coli. Ogr is a poor activator of the nuclease promoter in E. coli, but the related delta gene product from satellite phage P4 is highly effective. The presence of genes encoding a lysozyme and a putative porin or holin in the nucC operon suggests that nucC may be part of a cryptic prophage genome. The putative holin-like membrane protein is required in E. coli for extracellular secretion of the S. marcescens nuclease.
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PMID:Regulation of the Serratia marcescens extracellular nuclease: positive control by a homolog of P2 Ogr encoded by a cryptic prophage. 859 95

We investigated the regulation of the MexEF-OprN multidrug efflux system of Pseudomonas aeruginosa, which is overexpressed in nfxC-type mutants and confers resistance to quinolones, chloramphenicol and trimethoprim. Sequencing of the DNA region upstream of the mexEF-oprN operon revealed the presence of an open reading frame (ORF) of 304 amino acids encoding a LysR-type transcriptional activator, termed MexT. By using T7-polymerase, a 34-kDa protein was expressed in Escherichia coli from a plasmid carrying the mexT gene. Expression of a mexE::lacZ fusion was 10-fold higher in nfxC-type mutants than in the wild-type strain; however, transcription of mexT as well as the mexT DNA region was unchanged. Located adjacent to mexT but transcribed in opposite direction, the beginning of an ORF termed qrh (quinone oxidoreductase homologue) was identified. Expression of a qrh::lacZ fusion was also found to be activated by MexT. Further, we present evidence for coregulation at the transcriptional and the posttranscriptional level between the MexEF-OprN efflux system and the OprD porin responsible for cross-resistance of nfxC-type mutants to carbapenem antibiotics.
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PMID:Characterization of MexT, the regulator of the MexE-MexF-OprN multidrug efflux system of Pseudomonas aeruginosa. 1051 18

The transmembrane transcriptional activators ToxR and TcpP modulate expression of Vibrio cholerae virulence factors by exerting control over toxT, which encodes the cytoplasmic transcriptional activator of the ctx, tcp, and acf virulence genes. However, ToxR, independently of TcpP and ToxT, activates and represses transcription of the genes encoding two outer-membrane porins, OmpU and OmpT. To determine the role of ToxR-dependent porin regulation in V. cholerae pathogenesis, the ToxR-activated ompU promoter was used to drive ompT transcription in a strain lacking OmpU. Likewise, the ToxR-repressed ompT promoter was used to drive ompU transcription in a strain lacking both ToxR and OmpT. This strategy allowed the generation of a toxR(+) strain that expresses OmpT in place of OmpU, and a toxR(-) strain that expresses OmpU in place of OmpT. Growth rates in the presence of bile salts and other anionic detergents were retarded for the toxR(+) V. cholerae expressing OmpT in place of OmpU, but increased in toxR(-) V. cholerae expressing OmpU in place of OmpT. Additionally, the toxR(+) V. cholerae expressing OmpT in place of OmpU expressed less cholera toxin and toxin-coregulated pilus, and this effect was shown to be caused by reduced toxT transcription in this strain. Finally, the toxR(+) V. cholerae expressing OmpT in place of OmpU was approximately 100-fold reduced in its ability to colonize the infant-mouse intestine. Our results indicate that ToxR-dependent modulation of the outer membrane porins OmpU and OmpT is critical for V. cholerae bile resistance, virulence factor expression, and intestinal colonization.
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PMID:Altered expression of the ToxR-regulated porins OmpU and OmpT diminishes Vibrio cholerae bile resistance, virulence factor expression, and intestinal colonization. 1094 96

The phytopathogenic Gram-negative bacteria Erwinia chrysanthemi secretes pectinases, which are able to degrade the pectic polymers of plant cell walls, and uses the degradation products as a carbon source for growth. We characterized a major outer membrane protein, KdgM, whose synthesis is strongly induced in the presence of pectic derivatives. The corresponding gene was characterized. Analysis of transcriptional fusions showed that the kdgM expression is controlled by the general repressor of pectinolytic genes, KdgR, by the repressor of hexuronate catabolism genes, ExuR, by the pectinase gene repressor, PecS, and by catabolite repression via the cyclic AMP receptor protein (CRP) transcriptional activator. A kdgM mutant is unable to grow on oligogalacturonides longer than trimers, and its virulence is affected. Electrophysiological experiments with planar lipid bilayers showed that KdgM behaves like a voltage-dependent porin that is slightly selective for anions and that exhibits fast block in the presence of trigalacturonate. In contrast to most porins, KdgM seems to be monomeric. KdgM has no homology with currently known porins, but proteins similar to KdgM are present in several bacteria. Therefore, these proteins might constitute a new family of porin channels.
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PMID:The oligogalacturonate-specific porin KdgM of Erwinia chrysanthemi belongs to a new porin family. 1177 48

Inducible mineralization of TSA (4-toluenesulphonate) by Comamonas testosteroni T-2 is initiated by a secondary transport system, followed by oxygenation and oxidation by TsaMBCD to 4-sulphobenzoate under the regulation of TsaR and TsaQ. Evidence is presented for a novel, presumably two-component transport system (TsaST). It is proposed that TsaT, an outer-membrane porin, formed an anion-selective channel that works in co-operation with the putative secondary transporter, TsaS, located in the inner membrane. tsaT was identified as a 1017-bp ORF (open reading frame) on plasmid pTSA upstream of the TSA-catabolic genes in the tsa operon. Expression of tsaT was regulated by TsaR, the transcriptional activator of the tsa regulon. The presence of tsaT was concomitant with the presence of the tsa operon in different TSA-degrading isolates. tsaT was expressed in Escherichia coli and was detected in the outer membrane. A 22-amino-acid leader peptide was identified. Purified protein reconstituted in lipid bilayer membranes formed anion-selective channels with a single-channel conductance of 3.5 nS in 1 M KCl. Downstream of tsaT, a constitutively expressed 720-bp ORF (tsaS) was identified. tsaS coded for a hydrophobic protein predicted to have six transmembrane helices and which is most likely localized in the cytoplasmic membrane. tsaS is adjacent to tsaT, but showed a different transcriptional profile.
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PMID:A novel outer-membrane anion channel (porin) as part of a putatively two-component transport system for 4-toluenesulphonate in Comamonas testosteroni T-2. 1517 49

Multidrug resistance (MDR) in Enterobacter aerogenes can be mediated by induction of MarA, which is triggered by certain antibiotics and phenolic compounds. In this study, we identified the gene encoding RamA, a 113-amino-acid regulatory protein belonging to the AraC-XylS transcriptional activator family, in the Enterobacter aerogenes ATCC 13048 type strain and in a clinical multiresistant isolate. Overexpression of RamA induced an MDR phenotype in drug-susceptible Escherichia coli JM109 and E. aerogenes ATCC 13048, as demonstrated by 2- to 16-fold-increased resistance to beta-lactams, tetracycline, chloramphenicol, and quinolones, a decrease in porin production, and increased production of AcrA, a component of the AcrAB-TolC drug efflux pump. We show that RamA enhances the transcription of the marRAB operon but is also able to induce an MDR phenotype in a mar-deleted strain. We demonstrate here that RamA is a transcriptional activator of the Mar regulon and is also a self-governing activator of the MDR cascade.
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PMID:RamA is an alternate activator of the multidrug resistance cascade in Enterobacter aerogenes. 1521 3

In Salmonella enterica serovar Typhimurium, the membrane-localized CadC is a transcriptional activator of the cadBA operon, which contributes to the acid tolerance response. Unlike in Escherichia coli, in which transcription of cadC is constitutive, in S. enterica serovar Typhimurium cadC expression is induced by low pH and lysine. Inactivation of cadC suppresses the acid-sensitive phenotype of a cadA mutation, suggesting the existence of other CadC-dependent genes in addition to the cadBA operon. Using a proteomic approach, we identified 8 of the putative CadC-induced proteins and 15 of the putative CadC-repressed proteins. The former include porin proteins OmpC and OmpF. The latter include proteins involved in glycolysis, energy production, and stress tolerance. To better understand the altered levels of OmpC and OmpF, we compared expression of ompR in S. enterica serovar Typhimurium wild-type and cadC mutant strains and determined that CadC exerted a negative influence on ompR transcription. Taken together, our findings strongly suggest that CadC may be a global regulator involved in the OmpR regulatory system during acid adaptation.
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PMID:CadC has a global translational effect during acid adaptation in Salmonella enterica serovar Typhimurium. 1720 22

Zinc (Zn) is a trace element essential for life but can be toxic if present in excess. While cells have import systems to guarantee a vital Zn intracellular concentration, they also rely on export systems to avoid lethal Zn overload. In particular, the opportunistic pathogen Pseudomonas aeruginosa possesses four Zn export systems: CadA, CzcCBA, CzcD, and YiiP. In this work, we compare the importance for bacterial survival of each export system at high Zn concentrations. We show that the P-type ATPase CadA, and the efflux pump CzcCBA are the main efflux systems affecting the bacterium tolerance to Zn. In addition, cadA and czcCBA genes expression kinetics revealed a hierarchical organization and interdependence. In the presence of high Zn concentrations, cadA expression is very rapidly induced (<1 min), while czcCBA expression occurs subsequently (>15 min). Our present data show that the fast responsiveness of cadA to Zn excess is due to its transcriptional activator, CadR, which is constitutively present on its promoter and promptly activating cadA gene expression upon Zn binding. Moreover, we showed that CadA is essential for a timely induction of the CzcCBA efflux system. Finally, we observed an induction of cadA and czcCBA efflux systems upon phagocytosis of P. aeruginosa by macrophages, in which a toxic metal boost is discharged into the phagolysosome to intoxicate microbes. Importantly, we demonstrated that the regulatory link between induction of the CzcCBA system and the repression of the OprD porin responsible for carbapenem antibiotic resistance, is maintained in the macrophage environment.
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PMID:The CzcCBA Efflux System Requires the CadA P-Type ATPase for Timely Expression Upon Zinc Excess in Pseudomonas aeruginosa. 3247 11


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