Project Summary/Abstract
Antibiotic resistance is a serious global health threat. Current antibiotics target essential bacterial processes
and impose strong selective pressure for resistance. Upon antibiotic treatment, the healthy microbiota are
reduced in both number and diversity, leading to serious health consequences such as Clostridium difficile
colitis. Moreover, resistant traits can be transferred to other microbes, leading to the spread of antibiotic
resistance. Using virulence blockers to target specific pathogenicity mechanisms, while leaving the microbiota
intact, is a promising strategy to reduce resistance. This proposal will identify molecular target of a newly
discovered the type III secretion system (T3SS) inhibitor, and explore their modes of action for further
optimization and development. I will assess structure – activity relationship to optimize the T3SS inhibitors,
cyclic pepeptomers, and use affinity based method to identify their molecular targets in Pseudomonas
aeruginosa. Besides, target-based drug discovery offers the advantage of being low cost and less time
consuming. With the availability of high-resolution structure and development of algorithms to predict binding
affinity and poses of small molecules to its protein target, virtual screening can provide lead for optimization.
ExoU, an effector with phospholipase A2 activity, is the major effector in P. aeruginosa, one of six ESKAPE
pathogens which cause the majority of nosocomial infections in the U.S. and “escape” antimicrobial drugs.
ExoU has a serine/aspartate catalytic dyad and a separate cofactor-binding domain required for activation of
the enzyme. ExoU is highly toxic, associated with acute infection, antibiotic resistance and severe outcome in
patents. Delay ExoU expression can increase mice survival. Thus we set out to find ExoU inhibitors as a
strategy to treat acute infection and reduce resistance. We will identify ExoU inhibitors that 1) inhibit enzymatic
activity by targeting its catalytic residue serine, or 2) bind to the membrane localization domain which will
prevent ExoU's activation by virtual screening. The inhibitors that show binding affinity to ExoU in isothermal
titration calorimetry assay, and prevent cell death caused by ExoU will be chosen for optimization. Structure of
inhibitor-bound proteins will be solved using X-ray crystallography. I believe that my team of mentors (Drs.
Stone and Ottemann), advisors (Dr. Rubin, expert in X-ray crystallography; Dr. Jacobson, expert in computer-
aided drug discovery) and collaborators (Dr. Lokey, an expert in macromolecule synthesis, Drs. Crews and
Linington, natural product chemists) will provide me support to successfully carry out this project. With the
biochemical techniques I will learn, the structures and new inhibitors I will obtain in the K99 phase, I will then
collaborate with Dr. Shaw (medicinal chemist) and Dr. Jacobson to optimize the candidate hits in my
independent phase. This project extends my skill set in biochemical methods and has the potential to provide
substantial momentum towards drug discovery, and development. These will serve as the foundation of a R01
proposal to be prepared upon the completion of the main stages of this research plan.