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  • Articles  (64,607)
  • Springer Nature  (63,835)
  • Blackwell Publishing Ltd  (772)
  • American Meteorological Society
  • International Union of Crystallography
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  • 2000-2004  (37,692)
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  • Medicine  (64,607)
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  • Articles  (64,607)
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  • 1
    Electronic Resource
    Electronic Resource
    Rv3133c/dosR is a transcription factor that mediates the hypoxic response of Mycobacterium tuberculosis (2003)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 48 (2003), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Unlike many pathogens that are overtly harmful to their hosts, Mycobacterium tuberculosis can persist for years within humans in a clinically latent state. Latency is often linked to hypoxic conditions within the host. Among M. tuberculosis genes induced by hypoxia is a putative transcription factor, Rv3133c/DosR. We performed targeted disruption of this locus followed by transcriptome analysis of wild-type and mutant bacilli. Nearly all the genes powerfully regulated by hypoxia require Rv3133c/DosR for their induction. Computer analysis identified a consensus motif, a variant of which is located upstream of nearly all M. tuberculosis genes rapidly induced by hypoxia. Further, Rv3133c/DosR binds to the two copies of this motif upstream of the hypoxic response gene alpha-crystallin. Mutations within the binding sites abolish both Rv3133c/DosR binding as well as hypoxic induction of a downstream reporter gene. Also, mutation experiments with Rv3133c/DosR confirmed sequence-based predictions that the C-terminus is responsible for DNA binding and that the aspartate at position 54 is essential for function. Together, these results demonstrate that Rv3133c/DosR is a transcription factor of the two-component response regulator class, and that it is the primary mediator of a hypoxic signal within M. tuberculosis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2003.03474.x
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  • 2
    Electronic Resource
    Electronic Resource
    ParG, a protein required for active partition of bacterial plasmids, has a dimeric ribbon–helix–helix structure (2003)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 50 (2003), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The ParG protein (8.6 kDa) is an essential component of the DNA partition complex of multidrug resistance plasmid TP228. ParG is a dimer in solution, interacts with DNA sequences upstream of the parFG genes and also with the ParF partition protein both in the absence and presence of target DNA. Here, the solution nuclear magnetic resonance structure of ParG is reported. The ParG dimer is composed of a folded domain formed by two closely intertwined C-terminal parts (residues 33–76), and two highly mobile tails consisting of N-terminal regions (residues 1–32). The folded part of ParG has the ribbon–helix–helix (RHH) architecture similar to that of the Arc/MetJ superfamily of DNA-binding transcriptional repressors, although the primary sequence similarity is very low. ParG interacts with DNA predominantly via its folded domain; this interaction is coupled with ParG oligomerization. The dimeric RHH structure of ParG suggests that it binds to DNA by inserting the double-stranded β-sheet into the major groove of DNA, in a manner similar to transcriptional repressors from the Arc/MetJ superfamily, and that ParG can function as a transcriptional repressor itself. A new classification of proteins belonging to the Arc/MetJ superfamily and ParG homologues is proposed, based on the location of a conserved positively charged residue at either the beginning or at the end of the β-strand which forms part of the DNA recognition motif.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2003.03750.x
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  • 3
    Electronic Resource
    Electronic Resource
    A CLC-type chloride channel gene is required for laccase activity and virulence in Cryptococcus neoformans (2003)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 50 (2003), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Laccase is a major virulence factor required for infection caused by the human pathogenic yeast Cryptococcus neoformans. However, cellular processes involved in the regulation and expression of laccase remain largely unknown in C. neoformans. Here we report the identification of a chloride channel gene CLC-A which is essential for laccase activity in C. neoformans. CLC-A shares homology to CLC-type voltage-gated chloride channels from other organisms; for example, 63% homology to GEF1, a chloride channel gene from Saccharomyces cerevisiae. A clc-a mutant, Mlac3, generated by insertional mutagenesis as well as a targeted Δclc-a mutant produced undetectable laccase in a liquid assay and produced no melanin on asparagine agar containing norepinephrine. Mlac3 was complemented with wild-type CLC-A which restored laccase activity and melanin biosynthesis. The clc-a mutants also showed reduced synthesis of another important virulence factor, capsule, and showed reduced growth at elevated pH. In addition, the clc-a mutation resulted in attenuated virulence in a mouse cryptococcosis model that was restored by complementation with wild-type CLC-A, indicating that the chloride channel plays an important role in the virulence of the organism. Further analysis revealed that the basis for absent laccase expression in the clc-a mutant was a laccase transcriptional defect that could be restored by adding exogenous copper. In conclusion, our findings show that CLC-A plays a role in the expression of two important virulence factors, capsule and laccase expression, which are required for virulence of the fungal pathogen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2003.03752.x
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  • 4
    Electronic Resource
    Electronic Resource
    Inactivation of the decay pathway initiated at an internal site by RNase E promotes poly(A)-dependent degradation of the rpsO mRNA in Escherichia coli (2003)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 50 (2003), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: In Escherichia coli, RNA degradation is mediated by endonucleolytic processes, frequently mediated by RNase E, and also by a poly(A)-dependent mechanism. The dominant pathway of decay of the rpsO transcripts is initiated by an RNase E cleavage occurring at a preferential site named M2. We demonstrate that mutations which prevent this cleavage slow down degradation by RNase E. All these mutations reduce the single-stranded character of nucleotides surrounding the cleavage site. Moreover, we identify two other cleavage sites which probably account for the slow RNase E-mediated degradation of the mutated mRNAs. Failure to stabilize the rpsO transcript by appending a 5′ hairpin indicates that RNase E is not recruited by the 5′ end of mRNA. The fact that nucleotide substitutions which prevent cleavage at M2 facilitate the poly(A)-dependent degradation of the rpsO transcripts suggest an interplay between the two mechanisms of decay. In the discussion, we speculate  that  a  structural  feature  located  in  the  vicinity of M2 could be an internal degradosome entry site promoting both RNase E cleavages and poly(A)-dependent degradation of the rpsO mRNA. We also discuss the role of poly(A)-dependent decay in mRNA metabolism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2003.03753.x
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  • 5
    Electronic Resource
    Electronic Resource
    From nose to lung: the regulation behind Streptococcus pneumoniae virulence factors (2003)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 50 (2003), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Streptococcus pneumoniae probably possesses a redundant set of factors required for colonization of the nasopharynx and invasive disease, because of its strict relationship with its human host and relatively small genome size (∼2.1 Mb). Nevertheless, transcriptional regulation of genes encoding factors required for in vivo growth is predicted to be important on two fronts: in the transition from carriage to invasive disease and within different microniches of the nasopharynx. The importance of both serotype-specific and host tissue-specific virulence factors during infection and disease has been highlighted by the recent identification of novel virulence factors in this organism coupled with the release of complete genome sequences from two strains. These studies add to the foundation of knowledge of classical S. pneumoniae virulence factors such as polysaccharide capsule and pneumolysin, which have well-documented roles in pathogenesis
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2003.03764.x
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  • 6
    Electronic Resource
    Electronic Resource
    The NblAI protein from the filamentous cyanobacterium Tolypothrix PCC 7601: regulation of its expression and interactions with phycobilisome components (2003)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 50 (2003), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Cyanobacteria respond to changes in light or nutrient availability by modifications in their photosynthetic light harvesting antenna. In unicellular cyanobacteria a small polypeptide (NblA) is required for phycobilisome degradation following environmental stresses. In the filamentous strain Tolypothrix sp. PCC 7601 the nblAI gene, encoding a NblA homologue, is located upstream of the operon coding for phycoerythrin (cpeBA). The nblAI transcripts all originate from a single transcription start point; their intracellular levels vary according to nitrogen regimes but not with light spectral quality. Using recombinant His-tagged NblAI protein, we found that in vitro NblAI has affinity for both phycocyanin and phycoerythrin subunits from Tolypothrix sp. PCC 7601, but not for allophycocyanin from this cyanobacterium or for phycobiliproteins from other cyanobacterial species. We also observed that although nblAI is mainly expressed under nitrogen starvation, NblAI polypeptides are always present in the cell; a significant portion of them co-purify with phycobilisome preparations but only if cells were grown under red light. Our data indicate that NblAI attaches to the phycobilisomes even under non-inducing conditions and suggest a preferential affinity of NblAI for phycocyanin.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2003.03768.x
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  • 7
    Electronic Resource
    Electronic Resource
    NarE: a novel ADP-ribosyltransferase from Neisseria meningitidis (2003)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 50 (2003), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Mono ADP-ribosyltransferases (ADPRTs) are a class of functionally conserved enzymes present in prokaryotic and eukaryotic organisms. In bacteria, these enzymes often act as potent toxins and play an important role in pathogenesis. Here we report a profile-based computational approach that, assisted by secondary structure predictions, has allowed the identification of a previously undiscovered ADP-ribosyltransferase in Neisseria meningitidis (NarE). NarE shows structural homologies with E. coli heat-labile enterotoxin (LT) and cholera toxin (CT) and possesses ADP-ribosylating and NAD-glycohydrolase activities. As in the case of LT and CT, NarE catalyses the transfer of the ADP-ribose moiety to arginine residues. Despite the absence of a signal peptide, the protein is efficiently exported into the periplasm of Neisseria. The narE gene is present in 25 out of 43 strains analysed, is always present in ET-5 and Lineage 3 but absent in ET-37 and Cluster A4 hypervirulent lineages. When present, the gene is 100% conserved in sequence and is inserted upstream of and co-transcribed with the lipoamide dehydrogenase E3 gene. Possible roles in the pathogenesis of N. meningitidis are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2003.03770.x
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  • 8
    Electronic Resource
    Electronic Resource
    A six amino acid deletion, partially overlapping the VanSB G2 ATP-binding motif, leads to constitutive glycopeptide resistance in VanB-type Enterococcus faecium (2003)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 50 (2003), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Enterococcus faecium clinical isolate BM4524, resistant to vancomycin and susceptible to teicoplanin, harboured a chromosomal vanB cluster, including the vanS B / vanR B two-component system regulatory genes. Enterococcus faecium strain BM4525, isolated two weeks later from the same patient, was resistant to high levels of both glycopeptides. The ddl gene of BM4525 had a 2 bp insertion leading to an impaired d -alanine: d -alanine ligase. Sequencing of the vanB operon in BM4525 also revealed an 18 bp deletion in the vanS B gene designated vanS BΔ . The resulting six amino acid deletion partially overlapped the G2 ATP-binding domain of the VanS BΔ histidine kinase leading to constitutive expression of the resistance genes. Sequence analysis indicated that the deletion occurred between two tandemly arranged heptanucleotide direct repeats, separated by 11 base-pairs. The VanS B , VanS BΔ and VanR B proteins were overproduced in Escherichia coli and purified. In vitro autophosphorylation of the VanS B and VanS BΔ histidine kinases and phosphotransfer to the VanR B response regulator did not differ significantly. However, VanS BΔ was deficient in VanR B phosphatase activity leading to accumulation of phosphorylated VanR B . Increased glycopeptide resistance in E. faecium BM4525 was therefore a result of the lack of production of d -alanyl- d -alanine ending pentapeptide and to constitutive synthesis of d -alanyl- d -lactate terminating peptidoglycan precursors, following loss of d -alanine: d -alanine ligase and of VanS B phosphatase activity respectively. We suggest that the heptanucleotide direct repeat in vanS B may favour the appearance of high level constitutively expressed vancomycin resistance through a ‘slippage’ type of genetic rearrangement in VanB-type strains.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2003.03771.x
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  • 9
    Electronic Resource
    Electronic Resource
    Streptococcus pneumoniae heat shock protein 70 does not induce human antibody responses during infection (2000)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS immunology and medical microbiology 29 (2000), S. 0 
    Details
    ISSN: 1574-695X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Mouse monoclonal antibodies (mAbs) were developed against Streptococcus pneumoniae in search for potential common pneumococcal proteins as vaccine antigens. mAb 230,B-9 (IgG1) reacted by immunoblotting with a 70-kDa protein which was isolated by immunoaffinity chromatography and subsequent preparative electrophoresis. N-terminal amino acid sequencing showed homology to that of heat shock protein 70 (hsp70). The hsp70 epitope reactive with mAb 230,B-9 was found in all the pneumococci examined as well as in other streptococci and enterococci. The epitope was not expressed in several other examined Gram-positive or -negative bacteria. Pneumococcal hsp70 has by other investigators been proposed to be a vaccine candidate. Binding experiments using flow cytometry showed that the epitope was not surface-exposed on live exponential phase grown S. pneumoniae. Human patient sera did not react with affinity-purified pneumococcal hsp70. Therefore the pneumococcal hsp70 does not seem to be of special interest in a vaccine formulation. The human sera contained antibodies to high molecular proteins co-purified with hsp70. Some of these proteins could be the pneumococcal surface protein A.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-695X.2000.tb01536.x
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  • 10
    Electronic Resource
    Electronic Resource
    Virulence of a Proteus mirabilis ATF isogenic mutant is not impaired in a mouse model of ascending urinary tract infection (2000)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS immunology and medical microbiology 29 (2000), S. 0 
    Details
    ISSN: 1574-695X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Proteus mirabilis, a common cause of urinary tract infection, produces a number of different fimbriae, including ambient temperature fimbriae (ATF). These fimbriae are optimally expressed at 23°C and their contribution to urinary tract infection has so far remained unknown. In the present study, a clinical isolate of P. mirabilis and an isogenic allelic replacement mutant unable to express ATF were tested for their ability to cause infection in the ascending urinary tract infection model in mice. The atf mutant colonised the urinary tract as well as the wild-type strain and was also able to outcompete the wild-type strain in a co-challenge experiment. Different non-clinical P. mirabilis isolates showed a reactive AtfA band after Western blot analysis using a polyclonal rabbit AtfA antiserum. These data together suggest that ATF does not play a role in P. mirabilis urinary tract infection.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-695X.2000.tb01516.x
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