title: Distinct structural features of Rex-family repressors to sense redox levels in anaerobes and aerobes.
abstract: The Rex-family repressors sense redox levels by alternative binding to NADH or NAD(+). Unlike other Rex proteins that regulate aerobic respiration, RSP controls ethanol fermentation in the obligate anaerobe Thermoanaerobacter ethanolicus JW200(T). It is also found in other anaerobic microorganisms. Here we present the crystal structures of apo-RSP, RSP/NADH and RSP/NAD(+)/DNA, which are the first structures of Rex-family members from an obligate anaerobe. RSP functions as a homodimer. It assumes an open conformation when bound to the operator DNA and a closed conformation when not DNA-bound. The DNA binds to the N-terminal winged-helix domain and the dinucleotide, either reduced or oxidized, binds to the C-terminal Rossmann-fold domain. The two distinct orientations of nicotinamide ring, anti in NADH and syn in NAD(+), give rise to two sets of protein-ligand interactions. Consequently, NADH binding makes RSP into a closed conformation, which does not bind to DNA. Both the conserved residues and the DNA specificity of RSP show a number of variations from those of the aerobic Rex, reflecting different structural bases for redox-sensing by the anaerobic and aerobic Rex-family members.
authors.affiliation: Industrial Enzymes National Engineering Laboratory, Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin 300308, China.
authors.forename: Yingying
authors.initials: Y
authors.lastname: Zheng
authors.affiliation: Institute of Biological Chemistry, Academia Sinica, Taipei 11529, Taiwan.
authors.forename: Tzu-Ping
authors.initials: TP
authors.lastname: Ko
authors.affiliation: Industrial Enzymes National Engineering Laboratory, Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin 300308, China.
authors.forename: Hong
authors.initials: H
authors.lastname: Sun
authors.affiliation: Industrial Enzymes National Engineering Laboratory, Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin 300308, China.
authors.forename: Chun-Hsiang
authors.initials: CH
authors.lastname: Huang
authors.affiliation: Biofuels Institute, School of Environment, Jiangsu University, Zhenjiang 212013, China.
authors.forename: Jianjun
authors.initials: J
authors.lastname: Pei
authors.affiliation: Biofuels Institute, School of Environment, Jiangsu University, Zhenjiang 212013, China.
authors.forename: Riyong
authors.initials: R
authors.lastname: Qiu
authors.affiliation: Institute of Biological Chemistry, Academia Sinica, Taipei 11529, Taiwan.
authors.forename: Andrew H-J
authors.initials: AH
authors.lastname: Wang
authors.affiliation: Department of Microbiology, University of Georgia, Athens, GA 30602-2605, USA.
authors.forename: Juergen
authors.initials: J
authors.lastname: Wiegel
authors.affiliation: Biofuels Institute, School of Environment, Jiangsu University, Zhenjiang 212013, China. Electronic address: weilanshao@gmail.com.
authors.forename: Weilan
authors.initials: W
authors.lastname: Shao
authors.affiliation: Industrial Enzymes National Engineering Laboratory, Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin 300308, China. Electronic address: guo_rt@tib.cas.cn.
authors.forename: Rey-Ting
authors.initials: RT
authors.lastname: Guo
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism*; D018360:Crystallography, X-Ray; D009243:NAD / Q000378:metabolism; D010084:Oxidation-Reduction; D011485:Protein Binding; D011487:Protein Conformation; D055503:Protein Multimerization; D012097:Repressor Proteins / Q000378:metabolism*; D046968:Thermoanaerobacter / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D012097:Repressor Proteins; D009243:NAD
keywords: Allosteric regulation; Anaerobic fermentation; DNA binding protein; Rossmann fold; Transcription regulation; Winged helix domain