Zheng Yingying, Ko Tzu-Ping, Yang Yunyun, Shao Weilan, Guo Rey-Ting
Industrial Enzymes National Engineering Laboratory, Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin 300308, China.
Institute of Biological Chemistry, Academia Sinica, Taipei 11529, Taiwan.
Biochem Biophys Res Commun. 2015 Jan 16;456(3):733-6. doi: 10.1016/j.bbrc.2014.12.049. Epub 2014 Dec 16.
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.
雷克斯家族阻遏蛋白通过与NADH或NAD⁺的选择性结合来感知氧化还原水平。RSP是嗜热栖热放线菌JW200(T)中雷克斯的同源物，在这种专性厌氧菌中调节乙醇发酵。二聚体阻遏蛋白以开放构象与DNA结合。RSP/α-NAD⁺复合物的晶体结构显示出一组不同的配体相互作用，这主要是由于烟酰胺部分的独特构型。带正电荷的环被Tyr102侧链覆盖，并与靠近螺旋α8 N端的硫酸根离子相互作用。因此，RSP二聚体可能被锁定在不与DNA结合的封闭构象中。然而，α-NAD⁺对RSP的亲和力并不高于β-NAD⁺。要将其用作调节阻遏蛋白的效应物，还需要改进。
