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  • 1
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Gonococcal porins (Por) from strains FA19 (Por-1, serogroup A), MS11 (Por-2, serogroup B) and FA6434 (Por-5, a hybrid porin containing epitopes from both serogroups), were expressed in Escherichia coli and purified under non-denaturing conditions. Porins were inserted into liposomes, and they were bound by monoclonal antibodies which bind native Por and intact gonococci, but not denatured Por. All three recombinant porins (rPor) were highly immunogenic in rabbits without additional adjuvant. The rPor antisera were specific for Por by Western blotting and whole-cell radioimmunoprecipitation and were broadly cross-reactive within serogroups. Post-immune, but not pre-immune, sera bound to intact gonococci, induced deposition of complement components C3 and C9 onto gonococcal membranes and increased association with and activation of human neutrophils. Gonococci were not killed in bactericidal assays, and there was no phagocytic killing with gonococci opsonized with recombinant antisera. Lack of killing in bactericidal assays was not caused by the presence of blocking antibodies to the outermembrane protein Rmp.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford UK : Blackwell Science Ltd
    Molecular microbiology 24 (1997), S. 0 
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Bordetella pertussis regulates expression of its virulence factors such as pertussis toxin (Ptx) via the bvg locus, which encodes a two-component system composed of a sensor protein, BvgS, and a transcription activator, BvgA. We used a ptx–lac fusion on the B. pertussis chromosome to analyse promoter activation by alteration of specific sequences upstream of and within the promoter. Our data demonstrate that a pair of heptanucleotide inverted repeats separated by a turn of the DNA helix within the upstream repeat region (centred around nucleotide −136.5) are crucial cis-activating elements, and probably represent the initial BvgA-binding site. In addition, we demonstrate that the sequence between these repeats and the promoter plays a role in activation. Our data are most consistent with a model of co-operative binding of BvgA dimers to this intervening region and interaction with RNA polymerase at the promoter to activate ptx transcription. In the core promoter region both the non-consensus 21 bp spacing and the specific sequence between the −35 and −10 elements are crucial for promoter activity.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Six synthetic 25-mer peptides corresponding to certain presumed surfaced-exposed regions of gonococcal porin protein I (PI) were made from strains FA19 (PIA) and MS11 (PIB). Four peptides were immunogenic in rabbits. Affinity-purified antisera against both PIA and PIB N-terminal peptides were bactericidal for homologous gonococci and many heterologous PI serovars. However, sialylation of gonococcal lipopolysaccharide (LPS) by growth of gonococci in the presence of cytidine monophosphate–neuraminic acid (CMP–NANA) abrogated the bactericidal activity of these antisera. Binding of anti-PI monoclonal antibodies to whole gonococci was reduced two- to fourfold by sialylation of LPS, suggesting that sialylation may inhibit bactericidal activity by masking porin epitopes. However, binding of anti-PII (Opa) monoclonal antibodies was not inhibited, yet complement-mediated killing was inhibited by sialylated LPS. Binding of complement components C3 and C9 was inhibited in the presence of either anti-PI or anti-PII monoclonals when gonococci were grown in the presence of CMP–NANA. Thus sialylation inhibited both anti-PI antibody binding and complement deposition, with a resultant decrease in bactericidal activity.
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  • 4
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract We constructed a Tn5 derivative for potential use in transposon mutagenesis of Neisseria gonorrhoeae. It was incorporated into the chromosome apparently at random following transformation, but the insertion events were dependent on a functional RecA and independent of a functional transposase. Furthermore, in most cases there was an incomplete transposon inserted with little or no IS50 insertion sequence. These observations suggest that TnJ transposition may not be possible in N. gonorrhoeae and that this organism may have an unexplored illegitimate recombination system.
    Type of Medium: Electronic Resource
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