MdaB and NfrA, Two Novel Reductases Important in the Survival and Persistence of the Major Enteropathogen Campylobacter jejuni

TY - JOUR

T1 - MdaB and NfrA, Two Novel Reductases Important in the Survival and Persistence of the Major Enteropathogen Campylobacter jejuni

AU - Nasher, Fauzy

AU - Taylor, Aidan J.

AU - Elmi, Abdi

AU - Lehri, Burhan

AU - Ijaz, Umer Z.

AU - Baker, Dave

AU - Goram, Richard

AU - Lynham, Steven

AU - Singh, Dipali

AU - Stabler, Richard

AU - Kelly, David J.

AU - Gundogdu, Ozan

AU - Wren, Brendan W.

N1 - Funding Information: This work was supported by Biotechnology and Biological Sciences Research Council Institute Strategic Program BB/R012504/1 constituent project BBS/E/F/000PR10349 to B.W.W. A.J.T was supported by BBSRC grant BB/S014497/1 to D.J.K. U.Z.I. is supported by NERC IRF NE/L011956/1. The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication. Publisher Copyright: Copyright © 2022 Nasher et al. This is an open-access article distributed under the terms of the Creative Commons Attribution 4.0 International license.

PY - 2022/1

Y1 - 2022/1

N2 - The paralogues RrpA and RrpB, which are members of the MarR family of DNA binding proteins, are important for the survival of the global bacterial foodborne pathogen Campylobacter jejuni under redox stress. We report that RrpA is a positive regulator of mdaB, encoding a flavin-dependent quinone reductase that contributes to the protection from redox stress mediated by structurally diverse quinones, while RrpB negatively regulates the expression of cj1555c (renamed nfrA for NADPH-flavin reductase A), encoding a flavin reductase. NfrA reduces riboflavin at a greater rate than its derivatives, suggesting that exogenous free flavins are the natural substrate. MdaB and NfrA both prefer NADPH as an electron donor. Cysteine substitution and posttranslational modification analyses indicated that RrpA and RrpB employ a cysteine-based redox switch. Complete genome sequence analyses revealed that mdaB is frequently found in Campylobacter and related Helicobacter spp., while nfrA is predominant in C. jejuni strains. Quinones and flavins are redox cycling agents secreted by a wide range of cell types that can form damaging superoxide by one-electron reactions. We propose a model for stress adaptation where MdaB and NfrA facilitate a two-electron reduction mechanism to the less toxic hydroquinones, thus aiding survival and persistence of this major pathogen. IMPORTANCE Changes in cellular redox potential result in alteration in the oxidation state of intracellular metabolites and enzymes; consequently, cells make adjustments that favor growth and survival. The work we present here answers some of the many questions that have remained elusive over the years of investigation into the enigmatic microaerophile bacterium Campylobacter jejuni. We employed molecular approaches to understand the regulation mechanisms and functional analyses to reveal the roles of two novel quinone and flavin reductases; both serve as major pools of cellular redox-active molecules. This work extends our knowledge on bacterial redox sensing mechanisms and the significance of hemostasis.

AB - The paralogues RrpA and RrpB, which are members of the MarR family of DNA binding proteins, are important for the survival of the global bacterial foodborne pathogen Campylobacter jejuni under redox stress. We report that RrpA is a positive regulator of mdaB, encoding a flavin-dependent quinone reductase that contributes to the protection from redox stress mediated by structurally diverse quinones, while RrpB negatively regulates the expression of cj1555c (renamed nfrA for NADPH-flavin reductase A), encoding a flavin reductase. NfrA reduces riboflavin at a greater rate than its derivatives, suggesting that exogenous free flavins are the natural substrate. MdaB and NfrA both prefer NADPH as an electron donor. Cysteine substitution and posttranslational modification analyses indicated that RrpA and RrpB employ a cysteine-based redox switch. Complete genome sequence analyses revealed that mdaB is frequently found in Campylobacter and related Helicobacter spp., while nfrA is predominant in C. jejuni strains. Quinones and flavins are redox cycling agents secreted by a wide range of cell types that can form damaging superoxide by one-electron reactions. We propose a model for stress adaptation where MdaB and NfrA facilitate a two-electron reduction mechanism to the less toxic hydroquinones, thus aiding survival and persistence of this major pathogen. IMPORTANCE Changes in cellular redox potential result in alteration in the oxidation state of intracellular metabolites and enzymes; consequently, cells make adjustments that favor growth and survival. The work we present here answers some of the many questions that have remained elusive over the years of investigation into the enigmatic microaerophile bacterium Campylobacter jejuni. We employed molecular approaches to understand the regulation mechanisms and functional analyses to reveal the roles of two novel quinone and flavin reductases; both serve as major pools of cellular redox-active molecules. This work extends our knowledge on bacterial redox sensing mechanisms and the significance of hemostasis.

KW - Campylobacter jejuni

KW - Flavins

KW - MarR-like regulators

KW - MdaB

KW - NfrA

KW - Quinones

KW - RrpA

KW - RrpB

UR - http://www.scopus.com/inward/record.url?scp=85123442262&partnerID=8YFLogxK

U2 - 10.1128/JB.00421-21

DO - 10.1128/JB.00421-21

M3 - Article

C2 - 34606373

AN - SCOPUS:85123442262

SN - 0021-9193

VL - 204

JO - Journal of Bacteriology

JF - Journal of Bacteriology

IS - 1

M1 - e00421-21

ER -