1 research outputs found
Mechanism of MenE Inhibition by Acyl-Adenylate Analogues and Discovery of Novel Antibacterial Agents
MenE
is an <i>o</i>-succinylbenzoyl-CoA (OSB-CoA) synthetase
in the bacterial menaquinone biosynthesis pathway and is a promising
target for the development of novel antibacterial agents. The enzyme
catalyzes CoA ligation via an acyl-adenylate intermediate, and we
have previously reported tight-binding inhibitors of MenE based on
stable acyl-sulfonyladenosine analogues of this intermediate, including
OSB-AMS (<b>1</b>), which has an IC<sub>50</sub> value of ≤25
nM for <i>Escherichia coli</i> MenE. Herein, we show that
OSB-AMS reduces menaquinone levels in <i>Staphylococcus aureus</i>, consistent with its proposed mechanism of action, despite the observation
that the antibacterial activity of OSB-AMS is ∼1000-fold lower
than the IC<sub>50</sub> for enzyme inhibition. To inform the synthesis
of MenE inhibitors with improved antibacterial activity, we have undertaken
a structure–activity relationship (SAR) study stimulated by
the knowledge that OSB-AMS
can adopt two isomeric forms in which the OSB side chain exists either
as an open-chain keto acid or a cyclic lactol. These studies revealed
that negatively charged analogues of the keto acid form bind, while
neutral analogues do not, consistent with the hypothesis that the
negatively
charged keto acid form of OSB-AMS is the active isomer.
X-ray crystallography and site-directed mutagenesis confirm the importance
of a conserved arginine for binding the OSB carboxylate. Although
most lactol isomers tested were inactive, a novel difluoroindanediol
inhibitor (<b>11</b>) with improved antibacterial activity was
discovered, providing a pathway toward the development of optimized
MenE inhibitors in the future