Structure-Based Discovery of a Novel Small-Molecule Inhibitor of Methicillin-Resistant S. aureus

The rapid emergence and dissemination of methicillin-resistant Staphylococcus aureus (MRSA) strains represents a major threat to public health. MRSA elaborates an arsenal of secreted host-damaging virulence factors to mediate pathogenicity and blunt immune defense. Panton-Valentine leukocidin (PVL) and -toxin are pore-forming cytotoxins of recognized importance in the development of invasive MRSA infection and are thus potential targets for antivirulence therapy. We report the X-ray crystal structures of PVL and -toxin in their soluble, monomeric and oligomeric, membrane-inserted pore states, in complex with n-tetradecylphosphocholine (C14PC). The structures reveal two evolutionarily conserved phosphatidylcholine binding mechanisms and their roles in modulating host cell attachment, oligomer assembly and membrane perforation. Moreover, we demonstrate that the soluble C14PC compound protects primary human immune cells in vitro against cytolysis by PVL and -toxin and hence may serve as the basis for the development of novel antivirulence agents to combat MRSA.