Characterisation of the bacterial Esx-1 protein secretion pathway

The ESX-1 protein secretion system is a general protein export pathway found in many Gram positive bacteria including the serious animal pathogens Mycobacterium bovis andStaphylococcus aureus. Previous studies have shown that this secretion pathway is essential for the virulence of both of these organisms. The ESX-1 export pathway shares a number of common components, but there are clear differences in the composition of the machinery between Actinobacteria (including Mycobacteria)and firmicutes (e.g S. aureus).

The aim of this project is a structure-function analysis of the ESX-1 protein secretion machinery from S. aureus. The composition of the machinery will be investigated using protein cross-linking and native level protein purification approaches, coupled with two-hybrid studies and co-purification studies. The sub-cellular localisation of the machinery will be determined using fluorescence microscopy, using GFP fusions to different protein components, or subunit specific antibodies. Finally, the structure of one or more of the components of the machinery may be determined using X-ray crystallography.

The Palmer and Hunter laboratories have been working together on theS. aureus ESX-1 system for the past 3 years and have many tools in place to allow timely progress, including antisera to most of the ESX-1 components, overexpressing clones and S. aureus esx-1deletion mutant strains.