Molecular characterisation of Region A of FnBPA from Staphylococcus aureus

Abstract

The surface-expressed fibronectin-binding proteins, FnBPA and FnBPB, of Staphylococcus aureus promote attachment to immobilised fibrinogen and elastin via the N-Terminal A region. The N2N3 subdomains of region A were found to contain the minimum ligand-binding activity. A model of the 3D structure of the N2N3 subdomains of FnBPA was created based on the crystal structure of a similar fibrinogen-binding protein, ClfA. This model allowed C-terminal truncates of rAFnBPA to be constructed. Those lacking the latching peptide and preceding hinge region were defective in binding both fibrinogen and elastin indicating that both ligands bind to FnBPA in a similar manner. Further support for this theory was the inhibition of bacteria expressing FnBPA from binding immobilised fibrinogen and elastin by using a monoclonal anti-rAFnBPA antibody and a peptide comprising the C-terminal residues of they chain of fibrinogen.