Grant: Operating Grant

The Type III secretion system (T3SS) is a needle-like apparatus of ~20 highly conserved proteins which provides a mechanism for the direct injection of bacterial virulence proteins through the inner and outer bacterial membranes into the host cell cytosol, a process essential for subsequent pathogenicity. The T3SS apparatus is an attractive target for antibacteial therapies as it is unique to pathogenic bacteria including those responsible for whooping cough, bubonic plague, typhoid fever and severe food and water borne dysentery. We are using a multi-disciplinary biophysical approach (including x-ray crystallography, Nuclear Magenetic Resonance, labeling/mass spectrometry and single particle Electron Microscopy) complimented by in vivo analysis of designed mutants (including secretion competence, localization and virulence assays) to characterize the overall architecture, key protein-protein interactions, and molecular mechanisms that drive this fascinating system. Many of the components of the T3SS are highly oligomerized and/or membrane associated proteins, which are particularly challenging to study at the molecular level and require the development of new approaches and methods to facilitate their characterization which we have undertaken. In addition we are using a similarly multidisciplinary approach to characterize the structure and mechanism of action of bacterial virulence proteins specifically injected into the host by the T3SS needle apparatus, alone and in complex with their molecular target(s) in the infected human host. Collectively, the high resolution structures of these key protein/protein complexes are being used as templates for the design of antimicrobials and vaccines that are specific for the many notorious pathogens that encode a T3SS.