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Streptococcal beta protein has separate binding sites for human factor H and IgA-Fc.

På svenska

Author

  • Thomas Areschoug
  • Margaretha Stålhammar-Carlemalm
  • Ingrid Karlsson
  • Gunnar Lindahl

Summary, in English

The group B streptococcus (GBS) is the most important cause of life-threatening bacterial infections in newborn infants. Protective immunity to GBS infection is elicited by several surface proteins, one of which, the beta protein, is known to bind human IgA-Fc. Here, we show that the beta protein also binds human factor H (FH), a negative regulator of complement activation. Absorption experiments with whole human plasma demonstrated binding of FH to a GBS strain expressing beta protein, but not to an isogenic beta-negative mutant. This binding was due to a direct interaction between beta and FH, as shown by experiments with purified proteins. Inhibition tests and studies with beta fragments demonstrated that FH and IgA-Fc bind to separate and non-overlapping regions in beta. Heparin, a known ligand for FH, specifically inhibited the binding between beta and FH, suggesting that FH has overlapping binding sites for beta and heparin. Bacteria-bound FH retained its complement regulatory activity, implying that beta-expressing GBS may use bound FH to evade complement attack. The finding that beta protein binds FH adds to a growing list of interactions between human pathogens and complement regulatory proteins, supporting the notion that these interactions are of general importance in bacterial pathogenesis.

Publishing year

2002

Language

English

Pages

12642-12648

Publication/Series

Journal of Biological Chemistry

Volume

277

Issue

15

Document type

Journal article

Publisher

American Society for Biochemistry and Molecular Biology

Topic

  • Microbiology in the medical area

Keywords

  • Binding Sites
  • Streptococcus/*metabolism
  • Non-U.S. Gov't
  • Support
  • Fc/blood/*metabolism
  • Antigens
  • CD/blood/*metabolism
  • Base Sequence
  • Bacterial Proteins/*metabolism
  • Receptors
  • Human
  • Complement Factor H/*metabolism
  • DNA Primers

Status

Published

ISBN/ISSN/Other

  • ISSN: 1083-351X