2 DIFFERENT GENES-CODING FOR FIBRONECTIN-BINDING PROTEINS FROM STREPTOCOCCUS-DYSGALACTIAE - THE COMPLETE NUCLEOTIDE-SEQUENCES AND CHARACTERIZATION OF THE BINDING DOMAINS

The binding of Streptococcus dysgalactiae to fibronectin involves fibr onetcin-binding protein(s) present on the bacterial surface. Previousl y, we reported the cloning of two different genes coding for cell-wall -associated fibronectin-binding proteins from S. dysgalactiae strain S 2 [Lindgren, P.-E., Speziale, R, McGavin, M. J., Monstein, H.-J., Hook , M., Visai, L., Kostiainen, T., Bozzini, S. & Lindberg, M. (1992) J. Biol. Chem. 267, 1924-1931]. The two genes, fnbA and fnbB, have now be en sequenced and the primary amino acid sequences of the two fibronect in-binding proteins, FnBA and FnBB, have been deduced. The two protein s have predicted molecular masses of 117 kDa and 122 kDa, respectively , and are organized in a similar way. The fibronectin-binding activiti es are localized in repeated motifs, 32-37 amino acids long, in the CO OH-terminal regions of the proteins. The two fibronectin-binding prote ins have heterologous amino acid sequences, except for the COOH-termin al ends which include the fibronectin-binding repeats. The fibronectin -binding regions of the genes have been fused to IgG-binding domains o f protein A, utilizing the IgG-binding capacity of the resulting fusio n proteins, to facilitate isolation of the fibronectin-binding domains .