Many bacteria have developed sophisticated mechanisms of protein transport across membranes. These macromolecular secretory systems play a pivotal role in microbial pathogenesis and are considered as promising targets for a new generation of anti-bacterial therapy. The ESX systems of Mycobacterium tuberculosis, an important human pathogen, secrete multiple proteins that are implicated in host-pathogen interactions. Although numerous components of the ESX systems have been identified, the structure of individual building blocks, the overall architecture of the system and the molecular mechanism of secretion are currently unknown.
In this project, we will determine the atomic structures of the key components of the systems. Specifically, we will determine the structures of essential ATPases EccC and EccA that have been implicated in interactions with secreted proteins and in powering the secretion process. We will also characterize the interactions of EccC and EccA with secreted proteins by biophysical and biochemical methods. Our studies will answer an important question regarding the ESX secretion system: how do ATPases drive the translocation of secreted proteins? We will also solve the structure of MycP, a membrane-associated subtilisin-like protease that is present in all characterized mycobacterial ESX systems and essential for secretion process. Moreover, the M. tuberculosis strain carrying a mutation in the catalytic residue of MycP1 protease is less virulent than a wild type strain during the chronic stage of infection, which makes MycP protease an attractive drug target for latent M. tuberculosis. We will develop the specific inhibitors of MycP protease, which may be lead to a novel class of anti-mycobacterial drugs.