A FIBRINOGEN-BINDING PROTEIN OF STAPHYLOCOCCUS-EPIDERMIDIS

The present study reports on fibrinogen (Fg) binding of Staphylococcus epidermidis, Adhesion of different S. epidermidis strains to immobili zed Fg was found to vary significantly between different strains, and the component responsible was found to be proteinaceous in nature. To further characterize the Fg-binding activity, a shotgun phage display library covering the S. epidermidis chromosome was constructed. By aff inity selection (panning) against immobilized Fg, a phagemid clone, pS EFG1, was isolated, which harbors an insert with an open reading frame of similar to 1.7 kilobases. Results from binding and inhibition expe riments demonstrated that the insert of pSEFG1 encodes a specific Fg-b inding protein. Furthermore, affinity-purified protein encoded by pSEF G1 completely inhibited adhesion of S. epidermidis to immobilized Fg. By additional cloning and DNA sequence analyses, the complete gene, te rmed fbe, was found to consist of an open reading frame of 3,276 nucle otides encoding a protein, called Fbe, with a deduced molecular mass o f similar to 119 kDa. With a second phage display library made from an other clinical isolate of S. epidermidis, it was possible to localize the Fg-binding region to a 331-amino-acid-long fragment. PCR analysis showed that the fbe gene was found in 40 of 43 clinical isolates of S. epidermidis. The overall organization of Fbe resembles those of other extracellular surface proteins of staphylococci and streptococci. Seq uence comparisons with earlier known proteins revealed that this prote in is related to an Fg-binding protein of Staphylococcus aureus called clumping factor.