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  • 1
    Electronic Resource
    Electronic Resource
    Human neutrophil response to recombinant neisserial Opa proteins (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 6 (1992), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Interactions of human neutrophils with recombinant Escherichia coli expressing gonococcal outer membrane Opa proteins were examined using chemiluminescent and biological assays. Seven opa loci from Neisseria gonorrhoeae MS11 4.8 were expressed as β-lactamase-Opa fusion proteins that contained all but the mature N-terminal amino acid of the full-length Opa protein fused to three N-terminal amino acids derived from the mature β-lactamase. The Opa fusion proteins were exported and assembled in the outer membrane of E. coli in a manner similar to that of Opa in N. gonorrhoeae, as evaluated by antibody binding and in situ proteolytic cleavage. All fusion proteins exhibited the characteristic heat-modifiable migration in SDS-polyacrylamide gel electrophoresis that typifies Opa proteins of neisseriae. Opa fusion proteins conferred on E. coli the ability to stimulate a chemiluminescent response from human neutrophils in the absence of antibody or complement. The nature of the response in terms of chemiluminescence, phagocytosis, and killing was in all cases analogous to that seen using N. gonorrhoeae expressing the equivalent Opa protein. Neither E. coli nor gonococci expressing OpaA elicited a response from neutrophils. Use of E. coli expressing Opa fusions should be useful in defining their biological activities and pathogenic roles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1992.tb01345.x
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  • 2
    Electronic Resource
    Electronic Resource
    H-DNA formation by the coding repeat elements of neisserial opa genes (1991)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 5 (1991), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The coding repeat region of opa genes from Neisseria gonorrhoeae and Neisseria meningitidis determines the expression state of their respective genes through high-frequency addition or deletion of pentanucleotide coding repeat units (CRs; CTTCT). In vitro analyses of cloned opa gene CR regions using single-strand specific nucleases, oligonucleotide protection experiments, and modifications of non-B-DNA residues indicate that the regions form structures resembling H-DNA under acidic conditions in the presence of negative supercoiling. The purine/pyrimidine strand bias and H-palindromic nature of the repeat region are consistent with sequence requirements for H-DNA formation. Sequences flanking the repeat elements are required to form the H-DNA structure in vitro as judged by the pattern of exposed non-B-DNA residues in CR sequences synthesized as oligonucleotides to form β-galactosidase::CR translational fusions. The fusions phase vary by addition and deletion of CR elements and the rate of phase variation increases upon induction of the fusion genes. The opa gene CR region is the first reported bacterial H-DNA structure and is unique in that it ties within the coding sequence for the gene.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1991.tb02081.x
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  • 3
    Electronic Resource
    Electronic Resource
    Expression and phase variation of gonococcal P.11 genes in Escherichia coli involves ribosomal frameshifting and slipped-strand mispairing (1989)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 3 (1989), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Expression and phase variation of Neisseria gonorr-hoeae P.ll genes in Escherichia coli viere studied using TnphoA fusions. Fusions were created in the P.llc gene of N. gonorrhoeae JS3 using λTnphoA-1 and were characterized by restriction digestion and dideoxy sequencing. Three fusions were chosen for further study; Tnp7 (fusion junction at mature amino acid 7), Tnp57 (amino acid 57), Tnp66 (amino acid 66). All fusions were in frame with the P.llc coding sequence but were out of frame with the purported initiation codon. All fusion constructions were shown to phase vary in E. coli in an analogous fashion to that seen in N. gonorrhoeae, i.e. phase changes (in a recA background) at a frequency of c. 10−3 accompanied by an alteration at the DNA level of the number of coding repeats (CRs). In vitro mutagenesis of the fusion constructions indicated that expression of out of frame P.ll genes in E. coli was probably the result of ribosomal frameshifting within the run of ‘A’ residues immediately preceding the CR region and not due to low-level false initiation at codons other than the ATG initiation codon (as had previously been suggested). The mechanism for P.llc::phoA phase variation appears to be related to the ‘slipped-strand mispairing’ mechanism responsible for frameshift mutations in a number of other bacterial genes containing short, direct, tandem repeats.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1989.tb00226.x
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  • 4
    Electronic Resource
    Electronic Resource
    Neisseria gonorrhoeae acquires mutations in analogous regions of gyrA and parC in fluoroquinolone-resistant isolates (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 14 (1994), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Neisseria gonorrhoeae homologues of gyrA and parC have been identified using hybridization probes generated from conserved regions of diverse gyrA genes. These genes have been tentatively identified as gyrA and parC, based on predicted amino acid sequence homologies to known GyrA homologues from numerous bacterial species and to ParC from Escherichia coli and Salmonella typhimurium. The gyrA gene maps to a physical location distant from the gyrB locus on the gonococcal chromosome, which is similar to the situation found in E. coli. The parC gene is not closely linked (i.e. greater than 9 kb) to an identifiable parE gene in N. gonorrhoeae. The gonococcal GyrA is slightly larger than its E. coli homologue and contains several small insertions near the O-terminus of the predicted open reading frame. A series of ciprofloxacin-resistant mutants were selected by passage of N. gonorrhoeae on increasing concentrations of the antibiotic. Sequential passage resulted in the selection of isolates with minimum inhibitory concentrations approximately 10000-fold higher than the parental strain. Mutations within gyrA resulted in low to moderate levels of resistance, while strains with high-level resistance acquired analogous mutations in both gyrA and parC. Resistance mutations were readily transferred between N. gonorrhoeae strains by transformation. The frequencies of transformation, resulting in different levels of ciprofloxacin resistance, further support the notion that both gyrA and parC genes are invoived in the establishment of extreme levels of ciprofloxacin resistance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1994.tb01297.x
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  • 5
    Electronic Resource
    Electronic Resource
    Surface structure of pathogenicAeromonas (1987)
    Springer
    Cellular and molecular life sciences 43 (1987), S. 371-372 
    Details
    ISSN: 1420-9071
    Keywords: Aeromonas ; pathogens ; lipopolysaccharide ; S-layers ; proteins ; surfaces ; fish disease
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01940413
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