Secretion of virulence determinants from Gram negative bacteria

The outer membrane (OM) of Gram negative bacteria is the interface between the bacterial cell and the environment. Many important virulence determinants of pathogenic bacteria are either embedded in this membrane or secreted across the membrane. The OM represents a second hydrophobic barrier through which surface proteins must be secreted and a number of different pathways, have evolved to mediate efficient surface localization from Gram negative bacteria. One common system used for export of fibrillar surface structures involved in adhesion to eukaryotic cells is the chaperone: usher system. In this pathway, a periplasmic chaperone traps and assists folding of a nascent fibrillar subunit as it is secreted across the IM. This complex is then targeted to the outer membrane translocator (or usher) where polymerization occurs to form extended surface pili or fibrillar structures. In our lab we have used assembly of the F1 fibrillar structure of Yersinia pestis as a model to understand details of the chaperone: usher system. These polymers of F1 collapse into an antiphagocytic capsule-like structure that promotes survival of the bacteria in the early stages of infection. It is also a key component of plague vaccines and detection kits. This project will use a combination of molecular, genetic and biochemical studies, complemented by collaborative structural studies, to understand the mechanism of the Y. pestis F1 assembly pathway and to optimize its vaccine potential.