A FIBRONECTIN-BINDING PROTEIN FROM STREPTOCOCCUS-EQUISIMILIS - CHARACTERIZATION OF THE GENE AND IDENTIFICATION OF THE BINDING DOMAIN

We have cloned and characterized a gene, fnb, from S. equisimilis, enc oding a fibronectin-binding protein, FnB. A genomic library containing chromosomal DNA from S. equisimilis strain Se165 in the pUC18 vector in E. coli TG1 was screened using a DNA fragment of the gene fnbB from S. dysgalactiae strain S2 as probe. The complete gene was sequenced. The molecular mass of the protein, calculated from the deduced amino a cid sequence is 120 kDa, which coincides with that determined by gel e lectrophoresis and Western blotting of the gene product. The fibronect in-binding activity was localized to a region of three repeated units, each 36 amino acids long. The COOH-terminal part of FnB from S. equis imilis, including the repeated Fn-binding domain, is very similar to t he corresponding part of FnBB from S. dysgalactiae, indicating a commo n origin of the regions encoding Fn-binding activity of the respective genes.