Ohr Protects Corynebacterium glutamicum against Organic Hydroperoxide Induced Oxidative Stress

Meiru Si,Jingyuan Guan,Xihui Shen,Yaoling Zhang,Wei Ding,Yao Wang,Xiao Xiao,Jianbo Wang,Muhammad Tausif Chaudhry,Luis Eduardo Soares Netto

doi:10.1371/journal.pone.0131634

Abstract

Ohr, a bacterial protein encoded by the Organic Hydroperoxide Resistance (ohr) gene, plays a critical role in resistance to organic hydroperoxides. In the present study, we show that the Cys-based thiol-dependent Ohr of Corynebacterium glutamicum decomposes organic hydroperoxides more efficiently than hydrogen peroxide. Replacement of either of the two Cys residues of Ohr by a Ser residue resulted in drastic loss of activity. The electron donors supporting regeneration of the peroxidase activity of the oxidized Ohr of C. glutamicum were principally lipoylated proteins (LpdA and Lpd/SucB). A Δohr mutant exhibited significantly decreased resistance to organic hydroperoxides and marked accumulation of reactive oxygen species (ROS) in vivo; protein carbonylation was also enhanced notably. The resistance to hydrogen peroxide also decreased, but protein carbonylation did not rise to any great extent. Together, the results unequivocally show that Ohr is essential for mediation of organic hydroperoxide resistance by C. glutamicum.

Highlights

Reactive oxygen species (ROS) are among the most potent threats to living organisms; ROS modulate the intrinsic balance between life and death [1]
Organic Hydroperoxide Resistance (Ohr) is located between base pairs 24,295 and 24,732 of the C. glutamicum genome, and it encodes a protein of 145 amino acid residues with a theoretical molecular mass of 14.9 kDa
Ohr shares 53%, 46%, and 48% amino acid sequence identity with the Ohr proteins of Vibrio cholerae, X. fastidiosa, and Deinococcus radiodurans, respectively, and the ohr gene is present as a single copy

Summary

Introduction

Reactive oxygen species (ROS) are among the most potent threats to living organisms; ROS modulate the intrinsic balance between life and death [1]. ROS, including hydroxyl radicals, singlet oxygen, and hydrogen peroxide, are by-products generated via aerobic metabolic processes or upon stress caused by external agents [2]. When ROS levels are significant, the protective systems of living organisms are destroyed, and nucleic acids, proteins, carbohydrates, and lipids are damaged. Pathogenic bacteria invading a host induce a burst of enzymatic ROS synthesis, and the host seeks to mount a defense [3]. Of the various types of ROS, organic hydroperoxides are toxic, partly because they can generate free organic radicals, which in turn react with membranes and other macromolecules to promote.

Methods

Results

Conclusion