title: Binding mode of the oxidized α-anomer of NAD+ to RSP, a Rex-family repressor.
abstract: The Rex-family repressors sense redox levels by alternative binding to NADH or NAD(+). RSP is the homologue of Rex in Thermoanaerobacter ethanolicus JW200(T) and regulates ethanol fermentation in this obligate anaerobe. The dimeric repressor binds to DNA by an open conformation. The crystal structure of RSP/α-NAD(+) complex shows a different set of ligand interactions mainly due to the unique configuration of the nicotinamide moiety. The positively charged ring is covered by the Tyr102 side chain and interacts with a sulfate ion adjacent to the N-terminus of helix α8. Consequently, the RSP dimer may be locked in a closed conformation that does not bind to DNA. However, α-NAD(+) does not show a higher affinity to RSP than β-NAD(+). It has to be improved for possible use as an effector in modulating the repressor.
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: College of Biotechnology, Tianjin University of Science and Technology, Tianjin 300457, China; Industrial Enzymes National Engineering Laboratory, Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin 300308, China.
authors.forename: Yunyun
authors.initials: Y
authors.lastname: Yang
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 / Q000737:chemistry*; D018360:Crystallography, X-Ray; D016370:Gene Products, rex / Q000737:chemistry*; D007536:Isomerism; D009243:NAD / Q000737:chemistry*; D010084:Oxidation-Reduction; D011485:Protein Binding; D011487:Protein Conformation; D055503:Protein Multimerization; D012097:Repressor Proteins / Q000737:chemistry*; D046968:Thermoanaerobacter / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D016370:Gene Products, rex; D012097:Repressor Proteins; D009243:NAD
keywords: Allosteric effector; Ethanol fermentation; Thermoanaerobacter ethanolicus; Transcription regulation