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

In English

Författare

  • 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.

Publiceringsår

2002

Språk

Engelska

Sidor

12642-12648

Publikation/Tidskrift/Serie

Journal of Biological Chemistry

Volym

277

Issue

15

Dokumenttyp

Artikel i tidskrift

Förlag

American Society for Biochemistry and Molecular Biology

Ämne

  • Microbiology in the medical area

Nyckelord

  • 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/Övrigt

  • ISSN: 1083-351X