Human C4-binding protein. I. Isolation and characterization

Scharfstein, Júlio; Ferreira, Arturo; Gigli, Irma; Nussenzweig, Victor

doi:10.1084/jem.148.1.207

Cited by 255 publications

(151 citation statements)

References 22 publications

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“…First, we tested whether C4BP purified from plasma consisting of seven ␣-chains and one ␤-chain will bind pili with the same apparent affinity as the recombinant C4BP that is composed exclusively of ␣-chains. ␣-Chains are known to bind C4b (17), heparin (41), Bordetella pertussis (24), Streptococcus pyogenes (23), and serum amyloid P component (42), whereas ␤-chain binds anticoagulant protein S (18). We found that both forms of C4BP bound to pili with similar affinities, implying that ␣-chains confer the ability to bind gonococcal pili.…”

Section: Discussionmentioning

confidence: 99%

“…They are present mainly, but not exclusively, in proteins involved in the activation and regulation of the complement system. One of these regulators is C4BP, a large plasma protein consisting of seven identical ␣-chains and one ␤-chain held together by disulfide bonds (17,18). The ␣-and ␤-chains consist of eight and three CCP domains, respectively, and have C-terminal domains involved in the polymerization of the molecule (19).…”

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confidence: 99%

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A Novel Interaction Between Type IV Pili ofNeisseria gonorrhoeaeand the Human Complement Regulator C4b-Binding Protein

Blom

Rytkönen

Vásquez

et al. 2001

The Journal of Immunology

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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 α-chains and one β-chain linked together with disulfide bridges. We found that pili bind to the α-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 α-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.

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Section: Discussionmentioning

confidence: 99%

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confidence: 99%

A Novel Interaction Between Type IV Pili ofNeisseria gonorrhoeaeand the Human Complement Regulator C4b-Binding Protein

Blom

Rytkönen

Vásquez

et al. 2001

The Journal of Immunology

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“…The predominant isoform of C4BP has seven ␣-chains each containing eight complement control protein (CCP) modules (or short consensus repeats) and a single ␤-chain with three CCP modules (22,23). Transmission electron microscopy indicated that up to six molecules of C4b bind to one molecule of C4BP at the distal (N-terminal) ends of the seven ␣-chains (2).…”

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confidence: 99%

Human C4b-binding Protein, Structural Basis for Interaction with Streptococcal M Protein, a Major Bacterial Virulence Factor

Jenkins

Mark

Ball

et al. 2006

Journal of Biological Chemistry

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Human C4b-binding protein (C4BP) protects host tissue, and those pathogens able to hijack this plasma glycoprotein, from complement-mediated destruction. We now show that the first two complement control protein (CCP) modules of the C4BP ␣-chain, plus the four residues connecting them, are necessary and sufficient for binding a bacterial virulence factor, the Streptococcus pyogenes M4 (Arp4) protein. Structure determination by NMR reveals two tightly coupled CCP modules in an elongated arrangement within this region of C4BP. Chemical shift perturbation studies demonstrate that the N-terminal, hypervariable region of M4 binds to a site including strand 1 of CCP module 2. This interaction is accompanied by an intermodular reorientation within C4BP. We thus provide a detailed picture of an interaction whereby a pathogen evades complement.Bacteria that enter human blood or tissues will be opsonized by complement and destroyed by phagocytes unless they have a means of overcoming attack by the complement system. An extensively studied example of such a virulence mechanism is the ability of many Streptococcus pyogenes M proteins to bind the key human complement regulator C4b-binding protein (C4BP), 2 an interaction that endows the bacteria with resistance to phagocytosis (1). C4BP is a polymeric, soluble, glycoprotein (ϳ200 mg/liter in plasma) (2). The M proteins, classical bacterial virulence factors first recognized over 75 years ago (3), are fibrillar surface structures exhibiting antigenic variation within a 50 -100-amino acid residue hypervariable N terminus (4, 5). Expression of M protein is important for the ability of S. pyogenes to cause the diseases associated with this pathogen: acute pharyngitis and impetigo (6). Many other pathogens share the ability to sequester C4BP (7-12). Thus escape from complement attack by hijacking of C4BP is emerging as a widespread contributor to immune evasion strategies and is a therapeutic target.The complement system, a vital molecular component of innate immunity, consists of plasma and cell-surface proteins that conspire to rid the body of infectious particles (13,14). Because complement is potentially harmful to host tissue it is tightly regulated. Like other members of the regulators of complement activation (RCA) protein family, the plasma protein C4BP acts upon the bimolecular C3 convertases that are the main drivers of the complement cascade. The C3 convertases cleave and thereby activate the third component of complement, C3, leading to deposition of C3b on the surface of an unprotected particle such as an invading microorganism. This process, known as opsonization, marks the particle as a target for phagocytosis. C3b also nucleates assembly of further convertase complexes and progression of the cascade toward formation of the membrane attack complex. C4BP regulates the C3 convertase of the classical pathway, a complex of C4b and C2a, by acting as a cofactor for the proteolysis of C4b (15, 16) and accelerating the decay of C4b⅐C2a complexes deposited on host cells (17...

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“…C4BP is a large protein (570 kDa) consisting of several polypeptides: seven identical ␣-chains and one ␤-chain (4,5). As shown by electron microscopy and biochemical studies, C4BP consists of a ϳ160-kDa central core that can be released by chymotrypsin treatment and several extended tentacles formed by the ␣-chains (6, 7).…”

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Human C4b-Binding Protein Has Overlapping, But Not Identical, Binding Sites for C4b and Streptococcal M Proteins

Blom

Berggård

Webb

et al. 2000

The Journal of Immunology

104

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Many strains of Streptococcus pyogenes bind C4b-binding protein (C4BP), an inhibitor of complement activation. The binding is mediated by surface M proteins in a fashion that has been suggested to mimic the binding of C4b. We have previously shown that a positively charged cluster at the interface between complement control protein domains 1 and 2 of C4BP α-chain is crucial for the C4b-C4BP interaction. To extend this observation, and to investigate the interaction with M proteins, we constructed and characterized a total of nine mutants of C4BP. We identified a key recognition surface for M proteins that overlaps with the C4b binding site because substitution of R64 and H67 by Gln dramatically reduces binding to both ligands. However, the analysis of all mutants indicates that the binding sites for C4b and M proteins are only overlapping, but not identical. Furthermore, M proteins were able to displace C4BP from immobilized C4b, whereas C4b only weakly affected binding of C4BP to immobilized M proteins. We found that the molecular mechanisms involved in these two interactions differ because the binding between M proteins and C4BP is relatively insensitive to salt in contrast to the C4BP-C4b binding. In addition, six mAbs directed against the α-chain interfered with C4b-C4BP interaction, whereas only two of them efficiently inhibited binding of C4BP to M proteins. Collectively, our results suggest that binding between C4b and C4BP is governed mostly by electrostatic interactions, while additional noncovalent forces cause tight binding of C4BP to streptococcal M proteins.

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Human C4-binding protein. I. Isolation and characterization

Cited by 255 publications

References 22 publications

A Novel Interaction Between Type IV Pili ofNeisseria gonorrhoeaeand the Human Complement Regulator C4b-Binding Protein

A Novel Interaction Between Type IV Pili ofNeisseria gonorrhoeaeand the Human Complement Regulator C4b-Binding Protein

Human C4b-binding Protein, Structural Basis for Interaction with Streptococcal M Protein, a Major Bacterial Virulence Factor

Human C4b-Binding Protein Has Overlapping, But Not Identical, Binding Sites for C4b and Streptococcal M Proteins

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