DESCRIPTION: Staphylococcus aureus has the ability to colonize and infect many different host tissues and cause a variety of infections that differ in severity and location. The tissue tropism of an infection is the consequence of expressed adhesins and availability of corresponding substrate molecules. Collagen-binding adhesins on different bacteria appear to be essential for the effective colonization of joint tissue in septic arthritis and the cornea and vitreous invasive endophthalmitis. A detailed structural analyses of collagen-binding MSCRAMMs is the goal of the current proposal. We will determine the importance of individual amino acid residues in an identified ligand-binding site of the S. aureus adhesin. A recombinant protein corresponding to a ligand-binding domain of this adhesin has been crystallized and its structure will now be solved. Further structural studies of different recombinant MSCRAMM domains are planned using a variety of biophysical methods. Surface plasmon resonance will be used to characterize the interaction of the MSCRAMM with different types of collagen. Conformational changes in the MSCRAMM upon ligand binding will be probed using a monoclonal antibody approach. Finally, we will try to identify MSCRAMM-binding sites in type I and type II collagen using a combination of biochemical and immunological techniques. The information gained in the proposed studies will form the foundation for the design of new antibacterial strategies targeting MSCRAMMs. Such developments are desperately needed since Gram-positive bacteria in particular are developing multi-antibiotic resistance and are surfacing once again as a threat to mankind.