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  • 1
    Electronic Resource
    Electronic Resource
    Potential role of two Helicobacter pylori relaxases in DNA transfer? (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
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.1998.01086.x
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  • 2
    Electronic Resource
    Electronic Resource
    PilC of Neisseria meningitidis is involved in class II pilus formation and restores pilus assembly, natural transformation competence and adherence to epithelial cells in PilC-deficient gonococci (1997)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 23 (1997), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Type 4 pili produced by the pathogenic Neisseria species constitute primary determinants for the adherence to host tissues. In addition to the major pilin subunit (PilE), neisserial pili contain the variable PilC proteins represented by two variant gene copies in most pathogenic Neisseria isolates. Based upon structural differences in the conserved regions of PilE, two pilus classes can be distinguished in Neisseria meningitidis. For class I pili found in both Neisseria gonorrhoeae and N. meningitidis, PilC proteins have been implicated in pilus assembly, natural transformation competence and adherence to epithelial cells. In this study, we used primers specific for the pilC2 gene of N. gonorrhoeae strain MS11 to amplify, by the polymerase chain reaction, and clone a homologous pilC gene from N. meningitidis strain A1493 which produces class II pili. This gene was sequenced and the deduced amino acid sequence showed 75.4% and 73.8% identity with the gonococcal PilC1 and PilC2, respectively. These values match the identity value of 74.1% calculated for the two N. gonorrhoeae MS11 PilC proteins, indicating a horizontal relationship between the N. gonorrhoeae and N. meningitidispilC genes. We provide evidence that PilC functions in meningococcal class II pilus assembly and adherence. Furthermore, expression of the cloned N. meningitidis pilC gene in a gonococcal pilC1,2 mutant restores pilus assembly, adherence to ME-180 epithelial cells, and transformation competence to the wild-type level. Thus, PilC proteins exhibit indistinguishable functions in the context of class I and class II pili.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.1997.2631630.x
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  • 3
    Electronic Resource
    Electronic Resource
    Opa binding to cellular CD66 receptors mediates the transcellular traversal of Neisseria gonorrhoeae across polarized T84 epithelial cell monolayers (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: We have analysed the capacity of the 11 phase-variable, opacity-associated (Opa) proteins encoded by Neisseria gonorrhoeae MS11 to mediate traversal across polarized monolayers of the human colonic carcinoma T84 cell line. Gonococci expressing either the heparan sulphate proteoglycan (HSPG) binding Opa protein (Opa50) or no Opa protein (Opa−) did not interact with the apical pole of T84 monolayers, whereas the 10 variant Opa proteins previously shown to bind CD66 receptors were found to mediate efficient gonococcal adherence and transepithelial traversal. Consistent with this, T84 cells were shown by reverse transcriptase–polymerase chain reaction (RT–PCR) and immunoblotting to co-express CD66a (BGP), CD66c (NCA) and CD66e (CEA). The recruitment of CD66 receptors by Opa-expressing gonococci indicates their involvement in mediating adherence to the surface of T84 cells, and these bacterial interactions could be inhibited completely using polyclonal antibodies cross-reacting with all of the CD66 proteins co-expressed on T84 cells. Consistent results were obtained when Opa proteins were expressed in Escherichia coli, suggesting that the Opa–CD66 interaction is sufficient to mediate bacterial traversal. Transcytosis of Opa-expressing N. gonorrhoeae or E. coli did not disrupt the barrier function of infected monolayers, as indicated by a sustained transepithelial electrical resistance (TEER) throughout the course of infection, and confocal laser scanning and electron microscopy both suggest a transcellular rather than a paracellular route of traversal across the monolayers. Parallels between the results seen here and previous work done with organ cultures confirm that T84 monolayers provide a valid model for studying neisserial interactions with the mucosal surface, and suggest that CD66 receptors contribute to this process in vivo.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.1998.01102.x
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  • 4
    Electronic Resource
    Electronic Resource
    A novel peptidoglycan-linked lipoprotein (ComL) that functions in natural transformation competence of Neisseria gonorrhoeae (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: A novel peptidoglycan-linked lipoprotein (ComL) has been identified which is required for efficient transformation of Neisseria gonorrhoeae by species-related DNA. Although most mutations in comL appear to be lethal, transposon shuttle mutagenesis was successful in generating a single viable comL mutant of N. gonorrhoeae strain MS11. This mutant, N457, exhibits a cratered and crinkled colony morphology and grows slower than wild-type MS11. However, as indicated by electron microscopy, this retardation is due to a small bacterial size rather than to a decreased generation time of the mutant bacteria. Complementation of N457 with an intact comL gene via the Hermes shuttle system fully reconstitutes bacterial size, colony morphology, and transformation competence of the wild-type strain. comL is a single-copy gene and maps downstream of the previously described comA gene It is transcribed in the opposite direction, probably using the same transcriptional terminator. ComL has a predicted size of 29 kDa and is synthesized in Escherichia coli under the control of its native promoter, which is highly conserved with the E. coli promoter consensus sequence. The 5′ end of the coding sequence reveals a lipoprotein secretion signal shown to be functional by gene fusion with alkaline phosphatase (phoA′ ). In E. coli, cloned ComL can be labelled with [3H]-palmitic acid, thus demonstrating its lipoproteinaceous nature. Palmitoylated ComL appears to be covalently bound to the murein sacculus of E. coli and N. gonorrhoeae since it resists boiling in 4% sodium dodecyl sulphate and is released only by lysozyme treatment. Homologous counterparts of the comL gene are found in Neisseriameningitidis as well as in several non-pathogenic Neisseria species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.1996.457984.x
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  • 5
    Electronic Resource
    Electronic Resource
    Common structural features of IgA1 protease-like outer membrane protein autotransporters (1995)
    Osney Mead, Oxford OX2 0EL, UK : Blackwell Science Ltd
    Molecular microbiology 18 (1995), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1995.mmi_18020378.x
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  • 6
    Electronic Resource
    Electronic Resource
    Mutagenesis of the Neisseria gonorrhoeae porin reduces invasion in epithelial cells and enhances phagocyte responsiveness (1999)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 31 (1999), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Porin (PorB), the major outer membrane protein of Neisseria gonorrhoeae, has been implicated in pathogenesis previously. However, the fact that porin deletion mutants are not viable has complicated investigations. Here, we describe a method of manipulating the porin gene site-specifically. N. gonorrhoeae MS11, which harbours the porB1B (P.1B) porin allele, was used to generate mutants carrying deletions in the surface loops 1 and 5. An 11-amino-acid deletion in loop 1 impaired Opa50-dependent invasion into human Chang epithelial cells, whereas loop 5 deletion exhibited no apparent phenotype. In a second approach, the complete gonococcal porB1B was replaced by the porBNla gene of Neisseria lactamica. Such mutants were unable to induce efficient uptake by epithelial cells but induced an enhanced respiratory response in HL60 phagocytic cells. The increased respiratory burst was accompanied by an enhanced phagocytic uptake of the mutant compared with the wild-type strain. Our data extend previous evidence for multiple central functions of PorB in the infection process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.1999.01230.x
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  • 7
    Electronic Resource
    Electronic Resource
    Differential Opa specificities for CD66 receptors influence tissue interactions and cellular response to Neisseria gonorrhoeae (1997)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 26 (1997), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The ability of all 11 variable opacity (Opa) proteins encoded by Neisseria gonorrhoeae MS11 to interact directly with the five CD66 antigens was determined. Transfected HeLa cell lines expressing individual CD66 antigens were infected with recombinant N. gonorrhoeae and Escherichia coli strains expressing defined Opas. Based upon the ability of these bacteria to bind and invade and to isolate specifically CD66 antigens from detergent-soluble extracts of the corresponding cell lines, distinct specificity groups of Opa interaction with CD66 were seen. Defining these specificity groups allowed us to assign a specific function for CD66a in the Opa-mediated interaction of gonococci with two different target cell types, which are both known to co-express multiple CD66 antigens. The competence of individual Opas to interact with CD66a was strictly correlated with their ability to induce an oxidative response by polymorphonuclear neutrophils. The same Opa specificity was observed for the level of gonococcal binding to primary endothelial cells after stimulation with TNFα, which was shown to increase the expression of CD66a rather than CD66e. As CD66e alone is expressed on other target tissues of gonococcal pathogenicity, Opa variation probably contributes to the cell tropism displayed by gonococci.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.1997.6342006.x
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  • 8
    Electronic Resource
    Electronic Resource
    Cloning and characterization of the Neisseria gonorrhoeae MS11 folC gene (1996)
    Springer
    Molecular genetics and genomics 250 (1996), S. 277-285 
    Details
    ISSN: 1617-4623
    Keywords: Key words Gonococcus ; Folic acid ; Dihydrofolate synthetase ; Folylpolyglutamate synthetase ; One-carbon metabolism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The gene coding for folylpoly-(γ)-glutamate synthetase (FPGS)-dihydrofolate synthetase (DHFS) of Neisseria gonorrhoeae (Ngo) has been cloned by functional complementation of an Escherichia coli folC mutant (SF4). The sequence encodes a 224-residue protein of 46.4 kDa. It shows 46% identity to the E. coli FPGS-DHFS and 29% identity to the FPGS of Lactobacillus casei. Sequence comparisons between the three genes reveal regions of high homology, including ATP binding sites required for bifunctionality, all of which may be important for FPGS activity. In contrast to L. casei FPGS, the E. coli and Ngo enzymes share some additional regions which may be essential for DHFS activity. The products of Ngo folC and flanking genes were monitored by T7 promoter expression. Interestingly, deletion of the upstream folI gene, which encodes a 16.5 kDa protein, abolishes the capacity of folC to complement E. coli SF4 to the wild-type phenotype. The ability to complement can be restored by folI provided in trans. Unlike folC mutants, gonococcal folI mutants are viable and display no apparent phenotype. Thus, in contrast to E. coli, Ngo folC is expressed at a sufficiently high level from its own promoter, in the absence of FolI. This study provides the first insights into the genetic complexity of one-carbon metabolism in Ngo.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02174385
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  • 9
    Electronic Resource
    Electronic Resource
    Construction of hermes shuttle vectors: a versatile system useful for genetic complementation of transformable and non-transformableNeisseria mutants (1996)
    Springer
    Molecular genetics and genomics 250 (1996), S. 558-569 
    Details
    ISSN: 1617-4623
    Keywords: Plasmid vector ; Conjugation ; Generalized mutagenesis ; Homologous recombination ; Natural transformation competence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A versatile shuttle system has been developed for genetic complementation with cloned genes of transformable and non-transformableNeisseria mutants. By random insertion of a selectable marker into the conjugativeNeisseria plasmidptetM25.2, a site within this plasmid was identified that is compatible with plasmid replication and with conjugative transfer of plasmid. Regions flanking the permissive insertion site of ptetM25.2 were cloned inEscherichia coli and served as a basis for the construction of the Hermes vectors. Hermes vectors are composed of anE. coli replicon that does not support autonomous replication inNeisseria, e.g. ColE1, p15A, orori fd, fused with a shuttle consisting of a selectable marker and a multiple cloning site flanked by the integration region of ptetM25.2. Complementation of a non-transformableNeisseria strain involves a three-step process: (i) insertion of the desired gene into a Hermes vector; (ii) transformation of Hermes into aNeisseria strain containing ptetM25.2 to create a hybrid ptetM25.2 via gene replacement by the Hermes shuttle cassette; and (iii) conjugative transfer of the hybrid ptetM25.2 into the finalNeisseria recipient. Several applications for the genetic manipulation of pathogenicNeisseriae are described.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02174444
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  • 10
    Electronic Resource
    Electronic Resource
    Tyrosine Phosphorylation of Moesin in Arachidonic Acid–Stimulated Human Platelets (1998)
    Springer
    Journal of thrombosis and thrombolysis 6 (1998), S. 117-124 
    Details
    ISSN: 1573-742X
    Keywords: moesin ; ezrin ; tyrosine phosphorylation ; arachidonic acid ; platelets
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Moesin, a member of the ezrin/radixin/moesin (ERM) family of cytoskeletal proteins, has been implicated in dynamic membrane-based processes such as the formation and stabilization of filopodia. Ezrin is known to be a substrate of tyrosine kinases in activated T cells and epithelial growth factor–stimulated A431 cells. For the closely related 77-kD protein moesin, which shares 72% identity with ezrin on the basis of their amino acid sequences, a reversible phosphorylation on tyrosine residues has not yet been described. Because our scanning electron microscopy studies revealed the appearance of multiple, up to 3 μm long filopodia on the surface of activated human platelets, we investigated the participation of moesin in dynamic shape changes on platelet stimulation with arachidonic acid. Antimoesin immunoprecipitates obtained under denaturing conditions from lysates of resting platelets contained only low amounts of tyrosine-phosphorylated moesin. In lysates of arachidonic acid–stimulated platelets, the level of tyrosine phosphorylation was significantly increased. This activation-dependent phosphorylation of moesin was verified by probing antiphosphotyrosine immunoprecipitates from unstimulated and stimulated platelets with antimoesin antibodies. Tyrosine-phosphorylated moesin was detectable only in the presence of the tyrosine phosphatase inhibitor vanadate, suggesting that a coordinated balance between kinase and phosphatase activities controls the steady-state level of moesin phosphorylation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008845421381
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