Identification of a Mycothiol-Dependent Nitroreductase from Mycobacterium tuberculosis.

Ana Negri,Deena A Oren,Gang Liu,James C Sacchettini,Kyu Y Rhee,Ben Gold,Thulasi Warrier,Haitao Li,Julia Roberts,Kristin Burns-Huang,Thijs Beuming,Selin Somersan-Karakaya,Ran Mu,Xiuju Jiang,Xiaojie Zhang,Hongyao Wang,Jie Wu,Joel Warren ,Yan Lv ,D Barman ,Jérémie Vendôme ,Thomas R Ioerger ,Carl Nathan ,Prisca Elis Javidnia

doi:10.1021/acsinfecdis.7b00111

Abstract

The success of Mycobacterium tuberculosis (Mtb) as a pathogen depends on the redundant and complex mechanisms it has evolved for resisting nitrosative and oxidative stresses inflicted by host immunity. Improving our understanding of these defense pathways can reveal vulnerable points in Mtb pathogenesis. In this study, we combined genetic, structural, computational, biochemical, and biophysical approaches to identify a novel enzyme class represented by Rv2466c. We show that Rv2466c is a mycothiol-dependent nitroreductase of Mtb and can reduce the nitro group of a novel mycobactericidal compound using mycothiol as a cofactor. In addition to its function as a nitroreductase, Rv2466c confers partial protection to menadione stress.

Highlights

After coexisting with humans for an estimated 70 000 years,[1] Mycobacterium tuberculosis (Mtb) has emerged as the single leading cause of death from an infectious disease.[2]
Log phase bacteria were exposed to varying concentrations of 30a for 7 days and % inhibition was calculated on the basis of growth in vehicle (DMSO) wells
Bacterial and eukaryotic nitroreductases reduce polyaromatic nitro groups. Their exact role in Mtb pathogenesis is unclear, but presumably, they contribute to the antinitrosative defenses on which Mtb relies by detoxifying chemicals encountered in the host

Summary

Introduction

After coexisting with humans for an estimated 70 000 years,[1] Mycobacterium tuberculosis (Mtb) has emerged as the single leading cause of death from an infectious disease.[2]. With no other reservoir but humans, its only naturally transmitting host, Mtb must be adept at resisting stresses imposed by host immunity, including reactive oxygen species (ROS), reactive nitrogen species (RNS), and restricted access to oxygen, iron, and metabolizable sources of carbon. During adaptation to such stresses, Mtb alters its physiology and enters a slowly replicating or nonreplicating state[3,4] in which it becomes phenotypically relatively tolerant to most TB drugs.[5−7] Both host immunity[8] and conventional antimycobacterial chemotherapy[9] might be rendered more effective by inhibition of Mtb’s antioxidant and antinitrosative defenses. Data are means and SDs of triplicate wells and representative of two similar experiments. (D−F)

Methods

Results

Conclusion