SFS, a novel fibronectin-binding protein from Streptococcus equi, inhibitsthe binding between fibronectin and collagen

The obligate parasitic bacterium Streptococcus equi subsp. equi is the caus ative agent of strangles, a serious disease of the upper respiratory tract in horses. In this study we have, using shotgun phage display, cloned from S. equi subsp, equi and characterized a gene, called sfs, encoding a protei n termed SFS, representing a new type of fibronectin (Fn)-binding protein, The sfs gene was found to be present in all 50 isolates of S, equi subsp, e qui tested and in 41 of 48 S, equi subsp, zooepidemicus isolates tested. Th e sfs gene is down-regulated during growth in vitro compared to fnz, a prev iously characterized gene encoding an Fn-binding protein from S. equi subsp , zooepidemicus, Sequence comparisons revealed no similarities to previousl y characterized Fn-binding proteins, but high scores were obtained against collagen, Besides similarity due to the high content of glycine, serine, an d proline residues present in both proteins, there was a nine-residue motif present both in collagen and in the Fn-binding domain of SFS, By searching the Oklahoma S. pyogenes database, we found that this motif is also presen t in a potential cell surface protein from S. pyogenes, Protein SFS was fou nd to inhibit the binding between Fn and collagen in a concentration-depend ent way.