First-in-class rationally designed inhibitors of the SUF-like pathway of iron-sulfur cluster biosynthesis for treating infections caused by S. aureus and other Gram-positive bacteria - PROJECT SUMMARY/ABSTRACT
Antibiotic resistance is becoming increasingly catastrophic. Developing novel drugs that target essential ma-
chinery in bacteria for which there is not yet resistance is critical to expanding treatment options and reducing
the toll of infections. The long-term goal of this work is to develop drug candidates that target the SUF-like
pathway of iron-sulfur (Fe-S) cluster biosynthesis as a novel treatment for drug resistant infections caused by
Gram-positive bacteria. The SUF-like pathway was recently identified as a viable drug target, but a systematic
screen against any SUF proteins remains lacking. The overall objectives of this proposal, which build off a library
screen, are to characterize and optimize three structural classes of inhibitors of the SUF-like pathway that pos-
sess favorable pharmacokinetic and ADME properties and are effective against S. aureus, E. faecalis, and S.
pneumoniae. The specific target in the proposed research is the cysteine desulfurase from the SUF-like pathway,
SufS, which has >60% sequence identity between the three named species. The central hypothesis is that small
molecules can selectively occupy the SufS active site and alkylate the catalytic cysteine residue, thereby inhib-
iting cysteine desulfurase activity and causing reduced cell viability in Gram-positive bacteria. This hypothesis is
supported by preliminary data, including the screening of an acrylamide compound library against SufS from S.
aureus, which identified 18 hits that covalently modify SufS and inhibit cysteine desulfurase activity. The central
hypothesis will be tested through three specific aims: assess the (1) bioactivity and (2) biochemistry of the 18
hits and (3) synthetically modify the hits to improve potency and drug-likeness. In Aim 1, the inhibitors will be
assessed for their efficacy against S. aureus, E. faecalis, and S. pneumoniae; their specificity in S. aureus; and
their drug metabolism and pharmacokinetic properties. In Aim 2, the binding residue and binding mode of the
inhibitors will be determined using X-ray crystallography, and potency will be assessed using dose response
assays. In Aim 3, the best inhibitors will be synthetically modified to increase their potency and selectivity using
structure-guided drug design. The proposed research is innovative because it is the first known effort dedicated
to pursuing the SUF-like pathway as a drug target for new antibacterial agents, and it involves the first systematic
screening of a compound library against the SUF-like pathway. The proposed research is significant because
the results will provide a framework for developing novel broad-spectrum antibacterial agents, for which there is
not yet resistance, to treat infections from three Gram-positive infections, including S. aureus, E. faecalis, and
S. pneumoniae, which are all listed as serious threats by the Centers of Disease Control and Prevention. Addi-
tionally, this work will enhance our understanding of the effects of modulating the SUF-like pathway and lay the
foundation for identifying other targets that rely on the SUF-like pathway, such as M. tuberculosis and parasites
that causes malaria, thereby adding a powerful new tool to improve human health and well-being.
