Binding of C4b-binding protein: A molecular mechanism of serum resistance of Neisseria gonorrhoeae
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Summary, in English
We screened 29 strains of Neisseria gonorrhoeae and found 16/21 strains that resisted killing by normal human serum and 0/8 serum sensitive strains that bound the complement regulator, C4b-binding protein (C4bp). Microbial surfacebound C4bp demonstrated cofactor activity. We constructed gonococcal strains with hybrid porin (Por) molecules derived from each of the major serogroups (Por1A and Por1B) of N. gonorrhoeae, and showed that the loop 1 of Por1A is required for C4bp binding. Por1B loops 5 and 7 of serum-resistant gonococci together formed a negatively charged C4bp-binding domain. C4bpPor1B interactions were ionic in nature (inhibited by high salt or by heparin), whereas the C4bpPor1A bond was hydrophobic. Only recombinant C4bp mutant molecules containing the NH2-terminal -chain short consensus repeat (SCR1) bound to both Por1A and Por1B gonococci, suggesting that SCR1 contained Por binding sites. C4bp -chain monomers did not bind gonococci, indicating that the polymeric form of C4bp was required for binding. Using fAb fragments against C4bp SCR1, C4bp binding to Por1A and Por1B strains was inhibited in a complement-dependent serum bactericidal assay. This resulted in complete killing of these otherwise fully serum resistant strains in only 10 normal serum, underscoring the importance of C4bp in mediating gonococcal serum resistance.
Publishing year
2001
Language
English
Pages
281-295
Publication/Series
Journal of Experimental Medicine
Volume
193
Issue
3
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Document type
Journal article
Publisher
Rockefeller University Press
Topic
- Medicinal Chemistry
Status
Published
Research group
- Clinical Chemistry, Malmö
ISBN/ISSN/Other
- ISSN: 1540-9538