Automated docking studies provide insights into molecular determinants of ligand recognition by N-acetyl-1-D-myo-inosityl-2-amino-2-deoxy-α-D-glucopyranoside deacetylase (MshB)

Abstract

The metal-dependent deacetylase N-acetyl-1-D-myo-inosityl-2-amino-2-deoxy-α-D-glucopyranoside deacetylase (MshB) catalyzes the deacetylation of N-acetyl-1-D-myo-inosityl-2-amino-2-deoxy-α-D-glucopyranoside (GlcNAc-Ins), the committed step in mycothiol (MSH) biosynthesis. MSH is the thiol redox buffer used by mycobacteria to protect against oxidative damage and is involved in the detoxification of xenobiotics. As such, MshB is a target for the discovery of new drugs to treat tuberculosis (TB). While MshB substrate specificity and inhibitor activity have been probed extensively using enzyme kinetics, information regarding the molecular basis for the observed differences in substrate specificity and inhibitor activity is lacking. Herein we begin to examine the molecular determinants of MshB substrate specificity using automated docking studies with a set of known MshB substrates. Results from these studies offer insights into molecular recognition by MshB via identification of side chains and dynamic loops that may play roles in ligand binding. Additionally, results from these studies suggest that a hydrophobic cavity adjacent to the active site may be one important determinant of MshB substrate specificity. Importantly, this hydrophobic cavity may be advantageous for the design of MshB inhibitors with high affinity and specificity as potential TB drugs.

Keywords: MshB; deacetylase; metalloenzyme; molecular recognition; substrate specificity.