A novel interaction between type IV pili of Neisseria gonorrhoeae and the human complement regulator C4B-binding protein.
C4b-binding protein (C4BP) is an important plasma inhibitor of the classical pathway of complement activation. Several bacterial pathogens bind C4BP, which may contribute to their virulence. In the present report we demonstrate that isolated type IV pili from Neisseria gonorrhoeae bind human C4BP in a dose-dependent and saturable manner. C4BP consists of seven identical alpha-chains and one beta-chain linked together with disulfide bridges. We found that pili bind to the alpha-chain of C4BP, which is composed of eight homologous complement control protein (CCP) domains. From the results of an inhibition assay with C4b and a competition assay in which we tested mutants of C4BP lacking individual CCPs, we concluded that the binding area for pili is localized to CCP1 and CCP2 of the alpha-chain. The binding between pili and C4BP was abolished at 0.25 M NaCl, implying that it is based mostly on ionic interactions, similarly to what have been observed for C4b-C4BP binding. Furthermore, the N-terminal part of PilC, a structural component of pili, appeared to be responsible for binding of C4BP. Membrane cofactor protein, previously shown to be a receptor for pathogenic N. gonorrhoeae on the surface of epithelial cells, competed with C4BP for binding to pili only at high concentrations, suggesting that different parts of pili are involved in these two interactions. Accordingly, high concentrations of C4BP were required to inhibit binding of N. gonorrhoeae to Chang conjunctiva cells, and no inhibition of binding was observed with cervical epithelial cells.
Blom
A M
AM
Department of Clinical Chemistry, The Wallenberg Laboratory, Floor 6, Lund University, University Hospital Malmö, S-205 02 Malmö, Sweden. anna.blom@klkemi.mas.lu.se
Rytkönen
A
A
Vasquez
P
P
Lindahl
G
G
Dahlbäck
B
B
Jonsson
A B
AB
D015703:Antigens, CD / Q000235:genetics / Q000378:metabolism; D001426:Bacterial Proteins / Q000378:metabolism; D001667:Binding, Competitive / Q000235:genetics; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D002460:Cell Line; D015935:Complement C4b / Q000378:metabolism*; D003169:Complement Inactivator Proteins; D004847:Epithelial Cells / Q000378:metabolism / Q000382:microbiology; D036781:Fimbriae Proteins; D010861:Fimbriae, Bacterial / Q000145:classification / Q000378:metabolism*; D006023:Glycoproteins; D006531:HEPES / Q000494:pharmacology; D006801:Humans; D058619:Maltose-Binding Proteins; D051916:Membrane Cofactor Protein; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism; D009344:Neisseria gonorrhoeae / Q000378:metabolism*; D010446:Peptide Fragments / Q000378:metabolism; D011136:Polysorbates / Q000494:pharmacology; D011485:Protein Binding / Q000187:drug effects; D011951:Receptors, Complement / Q000097:blood / Q000302:isolation & purification / Q000378:metabolism* / Q000502:physiology; D012710:Serum Albumin, Bovine / Q000494:pharmacology; D012965:Sodium Chloride / Q000494:pharmacology; D012972:Sodium Hydroxide / Q000494:pharmacology; D014325:Tromethamine; D014407:Tumor Cells, Cultured
D015703:Antigens, CD; D001426:Bacterial Proteins; C497857:CD46 protein, human; D002352:Carrier Proteins; D003169:Complement Inactivator Proteins; D006023:Glycoproteins; D058619:Maltose-Binding Proteins; D051916:Membrane Cofactor Protein; D008562:Membrane Glycoproteins; D010446:Peptide Fragments; D011136:Polysorbates; D011951:Receptors, Complement; C079208:pilC protein, Neisseria gonorrhoeae; D014325:Tromethamine; D036781:Fimbriae Proteins; D012710:Serum Albumin, Bovine; D012965:Sodium Chloride; D012972:Sodium Hydroxide; D015935:Complement C4b; D006531:HEPES