Schematic representation of FnBPA from S. aureus 8325-4. (a) The N-terminus of FnBPA contains a signal sequence (S) followed by a 475 amino acid A domain, part of which is the binding site for fibrinogen and elastin. Adjacent to the A domain are eleven fibronectin-binding motifs that span residues 512–878 . The C-terminus of FnBPA contains a proline-rich repeat (PRR), wall (W) and membrane (M)-spanning domains, and the sortase recognition motif LPETG. (b) The FnBPA A domain is predicted to comprise three independently-folded sub-domains N1 (37–193), N2 (194–337), and N3 (338–511) . The His-tagged recombinant A domain isotype proteins (I – VII) analyzed during this study comprise the N2 and N3 sub-domains. Type-specific DNA probes used for typing fnbA genes from clinical isolates by DNA hybridization contain approximately 300 nucleotides that encode the central portion of the highly divergent N3 sub-domain. The diagram also indicates positions of general primers used for amplifying fnbA gene sequences that encode the entire A domain plus flanking sequence. These fnbA gene fragments were used as templates in DNA hybridization experiments with type specific probes, and for sequencing from a select number of strains.