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- Ram, Sanjay, et al.
(författare)
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Binding of C4b-binding protein: A molecular mechanism of serum resistance of Neisseria gonorrhoeae
- 2001
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Ingår i: Journal of Experimental Medicine. - : Rockefeller University Press. - 1540-9538 .- 0022-1007. ; 193:3, s. 281-295
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 2. |
- Ram, Sanjay, et al.
(författare)
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C4bp binding to porin mediates stable serum resistance of Neisseria gonorrhoeae
- 2001
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Ingår i: International Immunopharmacology. - 1878-1705. ; 1:3, s. 423-432
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Forskningsöversikt (refereegranskat)abstract
- Screening of 29 strains of Neisseria gonorrhoeae revealed that 16/21 serum resistant strains and 0/8 serum sensitive strains bound C4bp. suggesting that C4bp binding to gonococci could contribute to serum resistance. C4bp bound to gonococci retained cofactor (C4b-degrading) function. Using allelic exchange to construct strains with hybrid Por1A/B molecules, we demonstrate that the N-terminal loop (loop 1) of Por1A is required for C4bp binding. Serum resistant Por1B gonococcal strains also bind C4bp via their For molecule. Using allelic exchange and site-directed mutagenesis, we have shown that loops 5 and 7 together form a negatively charged C4bp binding domain. C4bp-Por1B interactions are ionic in nature (inhibited by high salt as well as by heparin), while the C4bp-Por1A bond is hydrophobic. mAbs directed against SCR1 of the alpha -chain of C4bp inhibit C4bp binding to both Por1A and Por1B. Furthermore. only recombinant C4bp mutant molecules that contain alpha -chain SCR1 bind both PorlA and Por1B gonococci, confirming that SCR1 contains For binding sites. C4bp alpha -chain monomers do not bind strains with either For molecule, suggesting that the polymeric form of C4bp is required for binding to gonococci, Inhibition of C4bp binding to serum resistant Por1A and Por1B strains in a serum bactericidal assay using fAb fragments against C4bp SCR1 results in complete killing at 30 min of otherwise fully serum resistant strains in only 10% normal serum, underscoring the role of C4bp in mediating gonococcal serum resistance. (C) 2001 Elsevier Science B,V. All rights reserved.
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