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  • 1
    Electronic Resource
    Electronic Resource
    PapB paralogues and their effect on the phase variation of type 1 fimbriae in Escherichia coli (2001)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 42 (2001), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Recent work has demonstrated that expression of type 1 fimbriae is repressed by PapB, a regulator of pyelonephritis-associated pili (P-pili). PapB belongs to family of related adhesin regulators, for which consensus residues required for DNA binding and oligomerization have been identified. Of the regulators tested in this study, PapB, SfaB (S-fimbriae) and PefB (Salmonella enterica serovar Typhimurium –plasmid-encoded fimbriae) repressed FimB-promoted off-to-on inversion of the fim switch, although complete repression was only demonstrated by PapB. DaaA, FaeB, FanA, FanB and ClpB had no effect on fim switching. In addition, only PapB stimulated FimE-promoted on-to-off inversion. Deletion analysis demonstrated that this specificity resides in the carboxy terminal of the protein, and not the amino terminal, with the central region being homologous among the family members. Exchange of Leu82 and Ile83 of PapB for the equivalent residues from the DaaA protein (Phe and Gln) within the carboxy terminal virtually abolished cross-talk activity. Whereas PapB can bind to a region around the left inverted repeat of the fim switch, DaaA and the PapB double mutant were effectively unable to bind this region. A previously characterized PapB DNA binding mutant also failed to bind to this region and failed to inhibit FimB activity at the fim switch. Thus, repression of fim expression appears unique to PapB and SfaB within E. coli and requires DNA binding involving amino acid residues located both within the homologous core and in the heterogeneous carboxy terminus. The variation in the carboxy terminus between the PapB family members explains their differential effects on fim. This mechanism of cross-talk seems restricted to the P and S family adhesins with type 1 fimbriae and may ensure variable and sequential expression of adhesins during urinary tract infections.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2001.02656.x
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  • 2
    Electronic Resource
    Electronic Resource
    In vitro analysis of mRNA processing by RNase E in the pap operon of Escherichia coli (1996)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 21 (1996), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Differential gene expression from operons encoding fimbrial adhesins in Escherichia coli involves processing and differential decay of polycistronic transcripts. Previous analyses of mRNA processing in vivo using ribonuclease mutants of E. coli have given different results with the different fimbrial gene systems tested. For the pap operon from uropathogenic E. coli, the results suggested that the mRNA processing is dependent on ribonuclease E (RNase E), whereas in other fimbrial operons with similar genetic organisation, the processing was concluded to be RNase E independent. We have developed an in vitro system allowing us to assess the cleavage of pap mRNA, to study the mRNA processing of a fimbrial operon in more detail, and to define the enzymatic activity and target. The results of this study establish that RNase E does indeed cleave the papBA intercistronic transcript. Analysis of the cleavage products reveals that in vitro RNase E can cleave the mRNA at other positions in addition to the site preferentially cleaved in vivo. The specificity of the cleavage pattern was assessed using transcripts derived from mutants with base substitutions near, or within, the major in vivo cleavage site. Such mutants have alternative cleavage sites. A common feature of the different cleavage sites is a high A/U nucleotide content, similar to other known RNase E cleavage sites. Features of the secondary structure of the papBA intercistronic mRNA were investigated using single-strand-specific and double-strand-specific nucleases. The secondary structure model derived from stability calculations and our results from the nuclease-probing experiments indicate that the positions subject to RNase E cleavage are mainly single stranded and flanked by more stable stem–loop structures. The results are consistent with the notion that an mRNA conformation exposing A/U-rich, non-paired regions constitutes the target, i.e. a flexible determinant, for processing by RNase E in the pap transcript. The findings are discussed in relation to the existence of a potential recognition site for RNase E and the analysis of RNase E cleavages in other RNA molecules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.1996.6121101.x
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  • 3
    Electronic Resource
    Electronic Resource
    Induction of haemolytic activity in Escherichia coli by the slyA gene product (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 20 (1996), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The Salmonella typhimurium protein SlyAST, originally described as a cytolysin, shows sequence similarities to several known bacterial regulatory proteins. A homologue to the slyASt gene has been localised to min 37 of the Eschericia coli K-12 chromosome and has been designated slyAEC When introduced in trans on a plasmid, the slyAEC gene conferred a haemolytic phenotype on wild-type but not clyA-knockout strains of E. coli K-12. The clyA gene encodes a novel haemolysin that is not expressed by wild-type E. coli under tested laboratory conditions. Western and Northern blot analyses, and DNA-band-shift assays support a model whereby the SlyAEC protein activates clyA expression by binding to the clyA promoter region, thereby supporting the sequence similarity data in suggesting that SlyAST is a haemolysin activator rather than being a haemolysin per se.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1996.tb02500.x
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  • 4
    Electronic Resource
    Electronic Resource
    Transfer RNA modification, temperature and DNA superhelicity have a common target in the regulatory network of the virulence of Shigella flexneri: the expression of the virF gene (2000)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 35 (2000), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Full expression of the virulence genes of Shigella flexneri requires the presence of two modified nucleosides in the tRNA [queuosine, Q34, present in the wobble position (position 34) and 2-methylthio-N6-isopentenyladenosine (ms2i6A37, adjacent to and 3′ of the anticodon)]. The synthesis of these two nucleosides depends on the products of the tgt and miaA genes respectively. We have shown that the intracellular concentration of the virulence-related transcriptional regulator VirF is reduced in the absence of either of these modified nucleosides. The intracellular concentration of VirF is correlated with the expression of the virulence genes. Overproduction of VirF in the tgt and the miaA mutants suppressed the less virulent (tgt) or the avirulent (miaA) phenotypes respectively, caused by the tRNA modification deficiency. This suggests that the primary result of undermodification of the tRNA is a poor translation of virF mRNA and not of any other mRNA whose product acts downstream of the action of VirF. Shigella showed no virulence phenotypes at 30°C, but forced synthesis of VirF at 30°C induced the virulence phenotype at this low temperature. In addition, removal of the known gene silencer H-NS by a mutation in its structural gene hns increased the synthesis of VirF at low temperature and thus induced a virulent phenotype at 30°C. Conversely, decreased expression of VirF at 37°C induced by the addition of novobiocin, a known inhibitor of gyrase, led to an avirulent phenotype. We conclude that tRNA modification, temperature and superhelicity have the same target – the expression of VirF – to influence the expression of the central regulatory gene virB and thereby the virulence of Shigella. These results further strengthen the suggestion that the concentration of VirF is the critical factor in the regulation of virulence in Shigella. In addition, they emphasize the role of the bacterial translational machinery in the regulation of the expression of virulence genes which appears here quantitatively as important as the well-established regulation on the transcriptional level.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2000.01767.x
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  • 5
    Electronic Resource
    Electronic Resource
    Oligomeric interaction of the PapB transcriptional regulator with the upstream activating region of pili adhesin gene promoters in Escherichia coli (1998)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 30 (1998), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Transcriptional regulation of the pap genes, which encode fimbrial adhesins in uropathogenic Escherichia coli, depends on an upstream activating region. This region contains binding sites for a transcription factor, PapB, which is a member of a growing family of putative regulatory proteins found in several virulence-associated fimbrial gene systems. To assess the nature of the PapB binding sites, we studied different naturally occurring variants and a number of in vitro constructed mutant binding sites. DNase I footprinting analysis and visualization of the PapB–DNA complex by atomic force microscopy showed that the protein occupied a DNA region of more than 50 bp. Purified PapB protein was shown to recognize a motif including a 9 bp repeat sequence containing T/A triplets at a conserved position. PapB binding was affected by distamycin, and the results were consistent with the possibility that the binding to DNA occurred through minor groove interaction. From these analyses and estimation of the relative number of PapB proteins per binding site, we suggest that PapB binds the DNA in an oligomeric fashion and may function as an architectural factor in the transcriptional control of adhesin expression.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.1998.01080.x
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  • 6
    Electronic Resource
    Electronic Resource
    Molecular analysis of the cytolytic protein ClyA (SheA) from Escherichia coli (1999)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 32 (1999), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Escherichia coli K-12 carries a gene for a protein denoted ClyA or SheA that can mediate a cytolytic phenotype. The ClyA protein is not expressed at detectable levels in most strains of E. coli, but overproduction suitable for purification was accomplished by cloning the structural gene in an hns mutant strain. Highly purified ClyA protein was cytotoxic to macrophage cells in culture and caused detachment and lysis of the mammalian cells. Results from osmotic protection assays were consistent with the suggestion that the protein formed pores with a diameter of up to 3 nm. Using Acholeplasma laidlawii cells and multilamellar liposomes, we studied the effect of ClyA on membranes with varying compositions and in the presence of different ions. ClyA induced cytolytic release of the fluorescent tracer from carboxyfluorescein-loaded liposomes, and the release was stimulated if cholesterol was present in the membranes whereas addition of calcium had no effect. Pretreatment of the ClyA protein with cholesterol inhibited the pore formation, suggesting that ClyA could bind to cholesterol. Efficient coprecipitation of ClyA with either cholesterol or 1,2,3-trioctadecanoylglycerol in aqueous solutions showed that ClyA directly interacted with the hydrophobic molecular aggregates. We tested the possible functional importance of selected ClyA protein regions by site-directed mutagenesis. Defined mutants of ClyA were obtained with alterations in postulated transmembrane structures in the central part and in a postulated membrane-targeting domain in the C-terminal part. Our results were consistent with the suggestion that particular amphiphilic segments are required for ClyA activity. We propose that these domains are necessary for ClyA to form pores.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.1999.01435.x
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  • 7
    Electronic Resource
    Electronic Resource
    YdgT, the Hha paralogue in Escherichia coli, forms heteromeric complexes with H-NS and StpA (2004)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 54 (2004), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: In enteric bacteria, proteins of the Hha/YmoA family play a role in the regulation of gene expression in response to environmental factors. Interaction of both Hha and YmoA with H-NS has been reported, and an Hha/H-NS complex has been shown to modulate expression in Escherichia coli of the haemolysin operon of plasmid pHly152. In addition to the hns gene, the chromosome of E. coli and other enteric bacteria also includes the stpA gene that encodes the StpA protein, an H-NS paralogue. We report here the identification of the Hha paralogue in E. coli, the YdgT protein. As Hha paralogue, YdgT appears to fulfil some of the functions reported for StpA as H-NS paralogue: YdgT is overexpressed in hha mutants and can compensate, at least partially, some of the hha-induced phenotypes. We also demonstrate that YdgT interacts both with H-NS and with StpA. Protein cross-linking studies showed that YdgT/H-NS heteromeric complexes are generated within the bacterial cell. The StpA protein, which is subjected to Lon-mediated turnover, was less stable in the absence of Hha or YdgT. Our findings suggest that Hha, YdgT and StpA may form complexes in vivo.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.2004.04268.x
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  • 8
    Electronic Resource
    Electronic Resource
    Runaway–Replication Plasmids as Tools to Produce Large Quantities of Proteins from Cloned Genes in Bacteria (1992)
    [s.l.] : Nature Publishing Company
    Nature biotechnology 10 (1992), S. 661-666 
    Details
    ISSN: 1546-1696
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: [Auszug] Here we review the properties and uses of runaway–replication vectors, a class of versatile plasmids discovered and developed in Escherichia coli. They are based on the IncFII plasmid, R1, in which an antisense RNA (CopA RNA) negatively controls the formation of a protein that is ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nbt0692-661
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  • 9
    Electronic Resource
    Electronic Resource
    An apoptotic response by J774 macrophage cells is common upon infection with diarrheagenic Escherichia coli (1999)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 172 (1999), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Representative strains of the different diarrheagenic Escherichia coli virotypes were tested for their potential cytotoxicity in the J774 macrophage cell line. All the seven virotypes of E. coli were cytotoxic to J774 macrophages, and in most cases the bacteria induced an apoptotic response. With the exception of the enterotoxigenic E. coli (ETEC) strain, all the other six virotypes caused induction of apoptosis as evidenced by quantitative analysis of the characteristic DNA fragmentation at the individual cell level. These results suggest that apoptosis could be one of the mechanisms contributing to the diarrheal disease development.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1999.tb13445.x
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  • 10
    Electronic Resource
    Electronic Resource
    Transcriptional silencing and thermoregulation of gene expression in Escherichia coli (1990)
    [s.l.] : Nature Publishing Group
    Nature 344 (1990), S. 682-685 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/344682a0
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