title: Identification and characterization of a new ligand-binding site in FnbB, a fibronectin-binding adhesin from Streptococcus dysgalactiae.
abstract: 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.
authors.affiliation: Department of Biochemistry, University of Pavia, Italy.
authors.forename: Livia
authors.initials: L
authors.lastname: Visai
authors.forename: Edda
authors.initials: E
authors.lastname: De Rossi
authors.forename: Viviana
authors.initials: V
authors.lastname: Valtulina
authors.forename: Fabrizia
authors.initials: F
authors.lastname: Casolini
authors.forename: Simonetta
authors.initials: S
authors.lastname: Rindi
authors.forename: Paola
authors.initials: P
authors.lastname: Guglierame
authors.forename: Giampiero
authors.initials: G
authors.lastname: Pietrocola
authors.forename: Vittorio
authors.initials: V
authors.lastname: Bellotti
authors.forename: Giovanna
authors.initials: G
authors.lastname: Riccardi
authors.forename: Pietro
authors.initials: P
authors.lastname: Speziale
mesh_terms: D018829:Adhesins, Bacterial / Q000737:chemistry / Q000276:immunology / Q000378:metabolism*; D000595:Amino Acid Sequence; D000918:Antibody Specificity; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism*; D001665:Binding Sites / Q000276:immunology; D002352:Carrier Proteins / Q000737:chemistry / Q000378:metabolism*; D018604:Epitope Mapping; D000939:Epitopes / Q000276:immunology; D005353:Fibronectins / Q000737:chemistry / Q000276:immunology; D008969:Molecular Sequence Data; D016415:Sequence Alignment; D013291:Streptococcus / Q000737:chemistry / Q000378:metabolism* / Q000472:pathogenicity
chemical_list: D018829:Adhesins, Bacterial; D001426:Bacterial Proteins; D002352:Carrier Proteins; D000939:Epitopes; D005353:Fibronectins; C078635:fibronectin-binding proteins, bacterial