Mechanisms of focal virulence factor assembly

Bacterial factors responsible for interaction with the environment or host are often found on the cell surface. In Gram positive bacteria, “housekeeping” sortase enzymes catalyze the attachment of some secreted proteins to the bacterial cell wall. In E. faecalis, Sortase C catalyzes the polymerization of newly secreted pilin monomers into pilus fibers, prior to Sortase A-mediated attachment of the pilus to the cell wall.

Thus, decoration of Gram positive cell surfaces is crucially dependent on coordination between cell wall synthesis, protein secretion, and sortase action. We have shown that these processes are spatially restricted to distinct sites on the cell surface in E. faecalis and that focal Sortase C localization is intimately linked to its efficient function in pilus biogenesis. E. faecalis pili are involved in biofilm formation, endocarditis, and urinary tract infections.

Using genetic and biochemical approaches, coupled with fluorescent and immuno-electron microscopy, we are exploring the molecular mechanisms that dictate focal localization of virulence factor assembly sites, using the pilus assembly platform as a model system.