Redox-Responsive Repressor Rex Modulates Alcohol Production and Oxidative Stress Tolerance in Clostridium acetobutylicum

Rex, a transcriptional repressor that modulates its DNA-binding activity in response to NADH/NAD+ ratio, has recently been found to play a role in the solventogenic shift of Clostridium acetobutylicum. Here, we combined a comparative genomic reconstruction of Rex regulons in 11 diverse clostridial s...

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Bibliographic Details
Published in:Journal of bacteriology 2014-11, Vol.196 (22), p.3949-3963
Main Authors: Zhang, Lei, Nie, Xiaoqun, Ravcheev, Dmitry A, Rodionov, Dmitry A, Sheng, Jia, Gu, Yang, Yang, Sheng, Jiang, Weihong, Yang, Chen
Format: Article
Language:English
Subjects:
alcohols
Alcohols - metabolism
Bacteria
Bacterial Proteins - genetics
Bacterial Proteins - metabolism
Bacteriology
Biosynthesis
Clostridium
Clostridium acetobutylicum
Clostridium acetobutylicum - genetics
Clostridium acetobutylicum - metabolism
Deoxyribonucleic acid
DNA
Fermentation
gene expression
Gene Expression Regulation, Bacterial - physiology
Genome, Bacterial
Genomes
Homeostasis
Hydrogen Peroxide
hydrogen production
mutants
Mutation
NAD
NAD (coenzyme)
nitrates
Oxidation-Reduction
Oxidative Stress
paraquat
Protein Binding
Regulon
repressor proteins
stress tolerance
Transcription Factors - genetics
Transcription Factors - metabolism
tricarboxylic acid cycle
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Summary:Rex, a transcriptional repressor that modulates its DNA-binding activity in response to NADH/NAD+ ratio, has recently been found to play a role in the solventogenic shift of Clostridium acetobutylicum. Here, we combined a comparative genomic reconstruction of Rex regulons in 11 diverse clostridial species with detailed experimental characterization of Rex-mediated regulation in C. acetobutylicum. The reconstructed Rex regulons in clostridia included the genes involved in fermentation, hydrogen production, the tricarboxylic acid cycle, NAD biosynthesis, nitrate and sulfite reduction, and CO2/CO fixation. The predicted Rex-binding sites in the genomes of Clostridium spp. were verified by in vitro binding assays with purified Rex protein. Novel members of the C. acetobutylicum Rex regulon were identified and experimentally validated by comparing the transcript levels between the wild-type and rex-inactivated mutant strains. Furthermore, the effects of exposure to methyl viologen or H2O2 on intracellular NADH and NAD+ concentrations, expression of Rex regulon genes, and physiology of the wild type and rex-inactivated mutant were comparatively analyzed. Our results indicate that Rex responds to NADH/NAD+ ratio in vivo to regulate gene expression and modulates fermentation product formation and oxidative stress tolerance in C. acetobutylicum. It is suggested that Rex plays an important role in maintaining NADH/NAD+ homeostasis in clostridia.
ISSN:0021-9193
1098-5530
DOI:10.1128/jb.02037-14