Identification and characterization of a new ligand-binding site in FnbB, a fibronectin-binding adhesin from Streptococcus dysgalactiae.
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.
Visai
Livia
L
Department of Biochemistry, University of Pavia, Italy.
De Rossi
Edda
E
Valtulina
Viviana
V
Casolini
Fabrizia
F
Rindi
Simonetta
S
Guglierame
Paola
P
Pietrocola
Giampiero
G
Bellotti
Vittorio
V
Riccardi
Giovanna
G
Speziale
Pietro
P
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
D018829:Adhesins, Bacterial; D001426:Bacterial Proteins; D002352:Carrier Proteins; D000939:Epitopes; D005353:Fibronectins; C078635:fibronectin-binding proteins, bacterial