title: Rex in Clostridium kluyveri is a global redox-sensing transcriptional regulator.
abstract: Clostridium kluyveri is unique in fermenting ethanol and acetate to butyrate, caproate, and H2. The genes encoding butyrate-producing enzymes, including electron-bifurcating butyryl-CoA dehydrogenase/electron transfer flavoprotein complex and NADH-dependent reduced ferredoxin:NADP(+) oxidoreductase, form a cluster, which is preceded by a gene annotated as the transcriptional regulator Rex. Northern blotting and RT-PCR experiments indicated that the gene cluster forms a large transcriptional unit that possibly includes several small transcriptional units. The deduced Rex protein contains a winged helix DNA-binding domain and a Rossmann fold potentially interacting with NAD(H). Bioinformatics analysis revealed that Rex can bind the promoter regions of numerous genes, which are involved in carbon and energy metabolism, including NADH oxidation, hydrogen production, ATP synthesis, butyrate formation, and succinate metabolism. Rex may regulate the transcription of genes encoding certain transcriptional regulators and transporters. Electrophoretic mobility shift and isothermal titration calorimetry assays revealed that Rex specifically formed protein-DNA complexes with the promoter regions of target genes, which could be inhibited by NADH but restored by an excess amount of NAD(+). These results suggest that Rex plays a key role in the carbon and energy metabolism of C. kluyveri as a global transcriptional regulator in response to the cellular NADH/NAD(+) ratio.
authors.affiliation: State Key Laboratory of Microbial Technology, School of life science, Shandong University, Jinan, People's Republic of China.
authors.forename: Liejie
authors.initials: L
authors.lastname: Hu
authors.affiliation: State Key Laboratory of Microbial Technology, School of life science, Shandong University, Jinan, People's Republic of China; Institute of Basic Medicine, Shandong Academy of Medical Science, Jinan, People's Republic of China.
authors.forename: Haiyan
authors.initials: H
authors.lastname: Huang
authors.affiliation: State Key Laboratory of Microbial Technology, School of life science, Shandong University, Jinan, People's Republic of China.
authors.forename: Hengxin
authors.initials: H
authors.lastname: Yuan
authors.affiliation: State Key Laboratory of Microbial Metabolism, School of Life Sciences & Biotechnology, Shanghai Jiao Tong University, Shanghai, People's Republic of China.
authors.forename: Fei
authors.initials: F
authors.lastname: Tao
authors.affiliation: Environment Research Institute, Shandong University, Jinan, People's Republic of China.
authors.forename: Huijun
authors.initials: H
authors.lastname: Xie
authors.affiliation: State Key Laboratory of Microbial Technology, School of life science, Shandong University, Jinan, People's Republic of China. Electronic address: shuningwang@sdu.edu.cn.
authors.forename: Shuning
authors.initials: S
authors.lastname: Wang
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D002087:Butyrates / Q000378:metabolism; D047010:Clostridium kluyveri / Q000235:genetics* / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial / Q000235:genetics*; D005798:Genes, Bacterial / Q000235:genetics*; D010084:Oxidation-Reduction
chemical_list: D001426:Bacterial Proteins; D002087:Butyrates
keywords: Butyrate synthesis; Clostridium kluyveri; Redox sensing; Rex; Transcriptional regulator