Identification and characterization of a new ligand-binding site in FnbB, a fibronectin-binding adhesin from Streptococcus dysgalactiae

Livia Visai, Edda De Rossi, Viviana Valtulina, Fabrizia Casolini, Simonetta Rindi, Paola Guglierame, Giampiero Pietrocola, Vittorio Bellotti, Giovanna Riccardi, Pietro Speziale

Research output: Contribution to journalArticlepeer-review


Streptococcus dysgalactiae S2, a bovine mastitis isolate, expresses the fibronectin (Fn)-binding adhesin FnbB. Here, we describe a new fibronectin-binding domain called UFnBD, located 100 amino acid N-terminal to the primary repetitive Fn-binding domain (FnBRD-B) of FnbB. UFnBD interacted with N-terminal region of Fn (N29) and this binding was mostly mediated by type I module pair 2-3 of N29 fragment, whereas FnBRD-B mainly bound to type I module pair 4-5. Furthermore, UFnBD inhibited adherence of S. dysgalactiae to Fn but at lower level as compared to FnBRD-B. UFnBD exclusively shared antigenic properties with the Fn-binding unit Du of FnbpA from Staphylococcus aureus but not with ligand-binding domains or motifs of other adhesins, while Fn-induced determinants of FnBRD-B and other adhesins appeared to be conformationally related. Consistent with this, a monoclonal antibody 7E11 generated from a mouse immunized with FnbB, and that recognized UFnBD did not cross-react with FnBRD-B. The epitope for 7E11 was mapped to 40 amino acid long segment within UFnBD and interaction between the antibody and the epitope was specifically induced by Fn or N29. A similar antibody epitope was observed in Streptococcus pyogenes strains suggesting the presence of an adhesin bearing epitope related to FnbB.

Original languageEnglish
Pages (from-to)173-183
Number of pages11
JournalBiochimica et Biophysica Acta - Proteins and Proteomics
Issue number1-2
Publication statusPublished - Mar 21 2003


  • Fibronectin-binding site
  • Monoclonal antibody
  • Streptococcus dysgalactiae

ASJC Scopus subject areas

  • Biochemistry
  • Biophysics
  • Genetics

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