Isolation and characterization of a putative collagen receptor from Staphylococcus aureus strain Cowan 1

In a previous study we demonstrated that cells of Staphylococcus aureus strain Cowan bind 125I-collagen in a receptor-ligand type of interaction (Speziale, P., Raucci, G., Visai, L., Switalski, L.M., Timpl, R., and Höök, M. (1986) J. Bacteriol. 167, 77-81). In the present communication we report on the isolation and preliminary characterization of a putative collagen receptor from a lysate of S. aureus strain Cowan. Antibodies raised against a collagen receptor positive strain inhibit the binding of 125I-collagen to bacterial cells, whereas antibodies raised against a collagen receptor negative strain were without effect. Solubilized cell surface components did not exhibit any measurable affinity for collagen-Sepharose. However, the inhibitory effect of the antibodies against bacterial cells was neutralized by the lysate from a receptor-positive but not receptor-negative strain. A collagen receptor assay was designed based on this observation and used to develop a receptor purification protocol involving anion exchange chromatography, ammonium sulfate precipitation, and gel chromatography. Using this procedure a protein with an apparent Mr of 135,000 was purified. This protein which was present on a collagen receptor-positive strain but not on a receptor-negative strain could completely neutralize the inhibitory activity of the antibodies raised against S. aureus strain Cowan. Furthermore, antibodies raised against the 135-kDa protein inhibited the binding of collagen to bacteria, and this protein is tentatively identified as a collagen receptor.