<p> <taxon tax_id="1280">Staphylococcus aureus</taxon> is a Gram-positive coccus that grows in clusters or pairs, and is the major cause of nosocomial infections due to its multiple antibiotic resistant nature. Patients who are immuno-compromised (e.g., those suffering from third degree burns or chronic illness) are at risk from deep staphylococcal infections, such as osteomyelitis and pneumonia. Most skin infections are also caused by this bacterium [<cite idref="PUB00008306"/>].</p><p>Many virulence mechanisms are employed by Staphylococci to induce pathogenesis: these can include polysaccharide capsules and exotoxins [<cite idref="PUB00008306"/>]. Examples of the latter are bi-component toxins, which involve the synergistic combination of an "S" and an "F" component [<cite idref="PUB00008890"/>]. These undergo conformational changes in their protein structure and form oligomeric pores in the target cell membrane upon recognition of certain host receptors. The main cells targeted are polymorphonuclear cells, monocytes, erythrocytes and macrophages. Examples of this protein family include: leucocidin, gamma-haemolysin and alpha-haemolysin.</p><p>Recently, the crystal structure of the S. aureus leucocidin "F" component (LukF) has been determined to 1.9A resolution [<cite idref="PUB00008891"/>]. This structure, which comprises a central 3-strand beta-sheet, with an N-terminal "latch", clarified the mechanism of virulence in the bi-component toxin. Further work using a different form of the leucocidin (LukF-PV) has suggested that it may be a representative fold for water-soluble transmembrane toxins [<cite idref="PUB00008892"/>].</p>