Isolation and characterization of a fibronectin receptor from Staphylococcus aureus

Attachment of bacteria to the host tissue is considered a first step in the development of many infections. Previous studies have shown that fibronectin, a protein shown to mediate substrate adhesion of eukaryotic cells, also binds to some pathogenic bacteria and mediates the tissue adherence of these prokaryotes. In the present communication, we report on the isolation and characterization of a fibronectin receptor from Staphylococcus aureus strain Newman. A 210-kDa fibronectin binding protein was isolated from a bacterial lysate by affinity chromatography followed by gel chromatography. Additional smaller peptides with fibronectin binding properties were also obtained. These peptides seem to represent degradation products of the large receptor protein since the former dominated when the purification was carried out in the absence of protease inhibitors. Furthermore, degradation of the purified receptor protein by staphylococcal V8 protease generated a large number of peptides that retained fibronectin binding activity. This observation also suggests that the large receptor protein contains several binding sites for fibronectin, and analysis of the binding of the 29-kDa amino-terminal fibronectin fragment to the 210-kDa receptor adsorbed in microtiter wells suggests that one receptor molecule can bind six to nine fibronectin molecules.