Fragment-based development of inhibitors of oxidative folding in Gram-negative bacteria

Speaker: Stephen Headey, Ph.D.

Research Fellow, Faculty of Pharmacy and Pharmaceutical Sciences

Medicinal Chemistry and Drug Action, Monash University

The continuing emergence of antibiotic resistant pathogenic bacteria is an alarming threat to human health, especially given that antibiotic development is failing to keep pace in recent years. Rather than aiming to kill pathogenic bacteria, a novel strategy that has recently been proposed is instead to target virulence. This approach has several potential benefits including greater species selectivity and perhaps less selective pressure for resistance. We have targeted the thiol-disulfide oxidoreductase enzyme DsbA which catalyzes the formation of disulfide bonds in the periplasm of Gram-negative bacteria. DsbA substrates include proteins that are bacterial virulence factors. In the absence of DsbA many of these proteins do not fold correctly, which renders the bacteria avirulent. We have used a biophysical screening approach to identify fragments that bind DsbA from E. coli. Elaboration of one of these fragments produced compounds that inhibit DsbA activity in vitro and reproduce a phenotype that is consistent with inhibition of DsbA in a cell based assay. Crystal structures reveal that the compounds bind in a pocket adjacent to the active site. This leads us to conclude that DsbA may be amenable to the development of novel antibacterial compounds that act by inhibiting bacterial virulence and provides important proof of principle in the feasibility of targeting virulence.