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  • 1
    Electronic Resource
    Electronic Resource
    Increased distal gene transcription by the elongation factor RfaH, a specialized homologue of NusG (1996)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 22 (1996), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The Escherichia coli RfaH protein is required for the expression of operons directing synthesis and export of the toxin haemolysin, the lipopolysaccharide core, and the F-factor sex pilus. Mutation of rfaH increases transcriptional polarity along all three operons. By demonstrating strong RfaH-dependent suppression of transcription polarity in vitro, we have established RfaH as a novel transcriptional activator, and we reveal that RfaH is a homologue of the essential protein NusG that modulates general transcriptional pausing and termination in prokaryotes. Full transcription of the distal genes from an upstream promoter required RfaH and the 5′ cis-acting ops element, both in vivo and in vitro. In vivo the requirement for the ops element was suppressed by overexpressing RfaH, and in vitro the presence of ops lowered the concentration of RfaH required to stimulate transcript elongation. We suggest that RfaH directs transcript elongation in an analogous way to NusG, but does so in a subset of bacterial operons primarily engaged in the production of extracellular components required for virulence and fertility.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.1996.d01-1726.x
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  • 2
    Electronic Resource
    Electronic Resource
    Suppression of transcription polarity in the Escherichia coli haemolysin operon by a short upstream element shared by polysaccharide and DNA transfer determinants (1996)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 19 (1996), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Expression of the Escherichia coli hlyCABD operon encoding synthesis, maturation and export of haemolysin toxin was strongly dependent upon a 35 bp DNA sequence, spanning the element GGCGGTAG, located 2 kbp upstream. When the hly operon was placed under the control of the inducible tac promoter, expression remained dependent upon this element, when transcribed in its native orientation 3′ of the promoter. The increase in ptac-directed transcription was strongest for the distal, export genes of the hly operon, and was particularly striking when ptac and the element were placed far upstream. The element did not influence transcript stability, and we suggest that it is a key component of a novel regulatory mechanism may suppresses transcription polarity within operons. The mechanism that be of widespread importance in bacterial gene expression because the 8 bp element is present in many Gram-negative species as an upstream component of operons encoding the production of toxins and the surface assembly of polysaccharides and components required for the conjugal transfer of DNA. We name it the ops element for operon polarity suppressor.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.1996.446951.x
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  • 3
    Electronic Resource
    Electronic Resource
    A novel mechanism for upregulation of the Escherichia coli K-12 hmp (flavohaemoglobin) gene by the ‘NO releaser’, S-nitrosoglutathione: nitrosation of homocysteine and modulation of MetR binding to the glyA-hmp intergenic region (1998)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 29 (1998), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The flavohaemoglobin gene, hmp, of Escherichia coli is upregulated by nitric oxide (NO) in a SoxRS-independent manner. We now show that hmp expression is also upregulated by S-nitrosoglutathione (GSNO, widely used as an NO releaser) and sodium nitroprusside (SNP, which is a NO+ donor). Elevated homocysteine (Hcy) levels, achieved either by adding Hcy extracellularly or using metE mutants, decreased hmp expression. Conversely, metC mutants (defective in Hcy synthesis) had higher levels of hmp expression. Mutations in metR abolished hmp induction by GSNO and SNP, and hmp expression became insensitive to Hcy. We propose that the previously documented modulation by Hcy of MetR binding to the glyA-hmp intergenic regulatory region regulates hmp transcription. Although two MetR binding sites are present in this region, only the higher affinity site proximal to hmp is required for hmp induction by GSNO and SNP. GSNO and SNP react with Hcy in vitro under physiologically relevant conditions of pH and temperature generating S-nitrosohomocysteine, although in the latter case this would be co-ordinated to the Fe in SNP as a stable species. The free S-nitrosocysteine generated in the reaction with GSNO breaks down to release NO more readily than via homolysis of GSNO. As GSNO and SNP upregulate hmp similarly, the NO released in the former case on reaction with homocysteine cannot be involved in hmp regulation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.1998.01000.x
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  • 4
    Electronic Resource
    Electronic Resource
    An ordered reaction mechanism for bacterial toxin acylation by the specialized acyltransferase HlyC: formation of a ternary complex with acylACP and protoxin substrates (1999)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 34 (1999), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The 110 kDa haemolysin protoxin (proHlyA) is activated in the Escherichia coli cytosol by acyl carrier protein-dependent fatty acylation of two internal lysine residues, directed by the co-synthesized protein HlyC. Using an in vitro maturation reaction containing purified protoxin peptides and acylACP, we show unambiguously that HlyC possesses an apparently unique acyltransferase activity fully described by Michaelis–Menten analysis. The Vmax of HlyC at saturating levels of both substrates was ≈ 115 nmol acyl group min−1 mg−1 with KmacylACP of 260 nM and KmproHlyA of 27 nM, kinetic parameters sufficient to explain why in vivo HlyC is required at a concentration equimolar to proHlyA. HlyC bound the fatty acyl group from acylACP to generate an acylated HlyC intermediate that was depleted in the presence of proHlyA, but enriched in the presence of proHlyA derivatives lacking acylation target sites. HlyC was also able to bind in vivo 4′-phosphopantetheine. Substitution of conserved amino acids that could act as putative covalent attachment sites did not prevent binding of the fatty acyl or 4′-phosphopantetheine groups. These data and substrate variation analyses suggest that the unique acylation reaction does not involve covalent attachment of fatty acid to the acyltransferase, but rather that it proceeds via a sequential ordered Bi–Bi reaction mechanism, requiring the formation of a non-covalent ternary acylACP–HlyC–proHlyA complex.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.1999.01648.x
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  • 5
    Electronic Resource
    Electronic Resource
    Zinc(II) tolerance in Escherichia coli K-12: evidence that the zntA gene (o732) encodes a cation transport ATPase (1997)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 25 (1997), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: A transposon (Tn10dCam) insertion mutant of Escherichia coli K-12 was isolated that exhibited hypersensitivity to zinc(II) and cadmium(II) and, to a lesser extent, cobalt(II) and nickel (II). The mutated gene, located between 75.5 and 76.2 min on the chromosome, is named zntA (for Zn(II) transport or tolerance). The metal-sensitive phenotype was complemented by a genomic DNA clone mapping at 3677.90–3684.60 kb on the physical map. Insertion of a kanamycin resistance (KnR) cassette at a Sal I site in a subcloned fragment generated a plasmid that partially complemented the zinc(II)-sensitive phenotype. DNA sequence analysis revealed that the KnR cassette was located within the putative promoter region of an ORF (o732 or yhhO) predicted to encode a protein of 732 amino acids, similar to cation transport P-type ATPases in the Cpx-type family. Inverse PCR and sequence analysis revealed that the Tn10dCam element was located within o732 in the genome of the zinc(II)-sensitive mutant. The zntA mutant had elevated amounts of intracellular and cell surface-bound Zn(II), consistent with the view that zntA+ encodes a zinc(II) efflux protein. Exposure of the zntA mutant to cobalt(II) and cadmium(II) also resulted in elevated levels of intracellular and cell surface-bound metal ions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1997.mmi518.x
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  • 6
    Electronic Resource
    Electronic Resource
    A motile but non-swarming mutant of Proteus mirabilis lacks FlgN, a facilitator of flagella filament assembly (1997)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 25 (1997), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: A TnphoA mutant of Proteus mirabilis was isolated, which had lost the ability to swarm, yet was still motile. The transposon had inserted into flgN, a flagella gene encoding a 147-amino-acid protein of undefined function. Proteus flgN is arranged in an operon with the class III anti-σ28 gene, flgM, flanked by the class II genes, flgA, flgBCD and flhBA, and a novel putative virulence-related gene. The flgN mutation caused a substantial reduction in cell surface-associated flagellin, particularly during differentiation to the normally hyperflagellated swarm cell. This was not due to an effect on flagella gene expression or a typical defect in the flagella export apparatus as there was no class III gene downregulation by FlgM feedback, or intracellular flagellin accumulation. Loss of FlgN nevertheless caused a severe reduction in the incorporation of pulse-labelled flagellin into the membrane/flagellum fraction of differentiating cells. Substantial amounts of both non-oligomeric flagellin and flagellin degradation products appeared in the extracellular medium, although the few mature filaments made by the mutant were no more sensitive to proteolysis than those of the wild type. FlgN appeared soluble and active in the cytosol. The data suggest that the function of FlgN is to facilitate the initiation of flagella filament assembly, a role that may be especially critical in attaining the much higher concentration of surface flagellin required for swarming. Proteus FlgN has leucine zipper-like motifs arranged on potential amphipathic helices, a feature conserved in cytosolic chaperones for the exported substrates of flagella-related type III virulence systems. While gel filtration of FlgN from the soluble cell fraction did not establish an interaction with flagellin, it indicated that FlgN may associate with an unknown component and/or form an oligomer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.1997.5021862.x
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  • 7
    Electronic Resource
    Electronic Resource
    Role of arginine-43 and arginine-69 of the Hin recombinase catalytic domain in the binding of Hin to the hix DNA recombination sites (1997)
    Oxford UK : Blackwell Science Ltd
    Molecular microbiology 24 (1997), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The Hin recombinase mediates the site-specific inversion of a segment of the Salmonella chromosome between two flanking 26 bp hix DNA recombination sites. Mutations in two amino acid residues, R43 and R69 of the catalytic domain of the Hin recombinase, were identified that can compensate for loss of binding resulting from elimination of certain major and minor groove contacts within the hix recombination sites. With one exception, the R43 and R69 mutants were also able to bind a hix sequence with an additional 4 bp added to the centre of the site, unlike wild-type Hin. Purified Hin mutants R43H and R69C had both partial cleavage and inversion activities in vitro while mutants R43L, R43C, R69S, and R69P had no detectable cleavage and inversion activities. These data support a model in which the catalytic domain plays a role in DNA-binding specificity, and suggest that the arginine residues at positions 43 and 69 function to position the Hin recombinase on the DNA for a step in the recombination reaction which occurs either at and/or prior to DNA cleavage.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.1997.4141789.x
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  • 8
    Electronic Resource
    Electronic Resource
    Biosynthesis of tripyrrole and β-lactam secondary metabolites in Serratia: integration of quorum sensing with multiple new regulatory components in the control of prodigiosin and carbapenem antibiotic production (2005)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 56 (2005), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Serratia sp. ATCC 39006 (39006) uses a complex hierarchical regulatory network allowing multiple inputs to be assessed before genes involved in secondary metabolite biosynthesis are expressed. This taxonomically ill-defined Serratia sp. produces a carbapenem antibiotic (Car; a β-lactam) and a red pigmented antibiotic, prodigiosin (Pig; a tripyrrole), which are controlled by the smaIR quorum sensing (QS) locus. SmaR is a repressor of Pig and Car when levels of N-acyl- l-homoserine lactones, produced by SmaI, are low. In this study, we demonstrate direct DNA binding of purified SmaR to the promoter of the Car biosynthetic genes and abolition of this binding by the QS ligand. We have also identified multiple new secondary metabolite regulators. QS controls production of secondary metabolites, at least in part, by modulating transcription of three genes encoding regulatory proteins, including a putative response regulator of the GacAS two-component signalling system family, a novel putative adenylate cyclase and Rap (regulator of antibiotic and pigment). Mutations in another gene encoding a novel predicted global regulator, pigP, are highly pleiotropic; PigP has a significant ‘master’ regulatory role in 39006 where it controls the transcription of six other regulators. The PigP protein and its homologues define a new family of regulators and are predicted to bind DNA via a helix-turn-helix domain. There are regulatory overlaps between the QS and PigP regulons that enable the information from different physiological cues to be funnelled into the control of secondary metabolite production.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.2005.04660.x
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  • 9
    Electronic Resource
    Electronic Resource
    Consumer Support Networks: assessment of need for consumer information and advice service (2005)
    Oxford, UK : Blackwell Science Ltd
    International journal of consumer studies 29 (2005), S. 0 
    Details
    ISSN: 1470-6431
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Economics
    Notes: Research evidence suggests that UK consumers are facing significant problems with goods and services and are in need of information and advice to avoid or redress such situations. Consumers are not always aware of their rights nor where they can access consumer advice services. In 2000, the Department of Trade and Industry launched the Consumer Support Network (CSN) programme in Great Britain to improve consumer access to expert, accurate and timely advice. One challenge faced by these Networks and many other agencies is to assess the needs of consumers for consumer information and advice services. A needs assessment is required as a key element in the effective planning and development of services in each Network at a local level. The focus of the needs assessment at the local level is to encourage Networks to consider suitable solutions to meet the needs of people in their communities. This paper provides a review of the development of Consumer Support Networks in Great Britain and discusses the importance of needs assessment to service providers such as CSNs and other agencies. It reveals the complexity associated with conducting effective needs assessments including the various aspects of needs, consumer segmentation and characteristics of consumer information and advice. Further research is being carried out at Queen Margaret University College, UK, with a view to the development of a scientific model for the assessment of need for consumer information and advice services.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1470-6431.2004.00421.x
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  • 10
    Electronic Resource
    Electronic Resource
    Editorial (2005)
    Oxford, UK : Blackwell Science Ltd
    International journal of consumer studies 29 (2005), S. 0 
    Details
    ISSN: 1470-6431
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Economics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1470-6431.2005.00430.x
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