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C4bp binding to porin mediates stable serum resistance of Neisseria gonorrhoeae
conference contributionposted on 16.02.2021, 05:33 by S Ram, Meabh Cullinane, AM Blom, S Gulati, DP McQuillen, R Boden, BG Monks, C O'Connell, C Elkins, MK Pangburn, B Dahlbäck, PA Rice
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 Por 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 α-chain of C4bp inhibit C4bp binding to both Por1A and Por1B. Furthermore, only recombinant C4bp mutant molecules that contain α-chain SCR1 bind both Por1A and Por1B gonococci, confirming that SCR1 contains Por binding sites. C4bp α-chain monomers do not bind strains with either Por 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. © 2001 Elsevier Science B.V.
PublisherELSEVIER SCIENCE BV
Name of conferenceXVIIIth International Complement Workshop
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Science & TechnologyLife Sciences & BiomedicineImmunologyPharmacology & PharmacyNeisseria gonorrhoeaeC4b-binding proteinporinserum resistanceHUMAN C4B-BINDING PROTEINPHENOTYPICALLY DETERMINED RESISTANCECOMPLEMENT REGULATOR C4BPSEROVAR-SPECIFIC IMMUNITYHUMAN C4-BINDING PROTEINASIALOGLYCOPROTEIN RECEPTORSEROLOGICAL CLASSIFICATIONMONOCLONAL-ANTIBODIESGONOCOCCAL-INFECTIONSIALIC-ACIDHumansGlycoproteinsPorinsImmunoglobulin MReceptors, ComplementBlood Bactericidal ActivityBinding SitesAmino Acid SequenceSequence Homology, Amino AcidPhenotypeMolecular Sequence DataComplement Inactivator ProteinsComplement C4In Vitro Techniques