文献类型： 外文期刊

作者： Han, Xiaodong ¹ ; Qian, Lei ¹ ; Zhang, Lianwen ⁴ ; Liu, Xinqi ¹ ;

作者机构： 1.Nankai Univ, Coll Life Sci, State Key Lab Med Chem Biol, Tianjin 300071, Peoples R China

2.Tianjin Acad Agr Sci, Tianjin Res Inst Forestry & Pomol, Tianjin 300192, Peoples R China

3.Shanxi Univ Tradit Chinese Med, Food & Pharmaceut Engn Inst, Taiyuan 030024, Peoples R China

4.Nankai Univ, Coll Pharm, Collaborat Innovat Ctr Biotherapy, Tianjin 300071, Peoples R China

5.Nankai Univ, Tianjin Key Lab Mol Drug Res, Tianjin 300071, Peoples R China

关键词： Nucleotide-rhamnose synthase/epimerase-reductase;Arabidopsis thaliana;Crystal structure;Active site

期刊名称：BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS （ 影响因子：3.036； 五年影响因子：2.969 ）

ISSN： 1570-9639

年卷期： 2015 年 1854 卷 10 期

页码：

收录情况： SCI

摘要： L-Rhamnose (Rha) is synthesized via a similar enzymatic pathway in bacteria, plants and fungi. In plants, nucleotide-rhamnose synthase/epimerase-reductase (NRS/ER) catalyzes the final step in the conversion of dTDP/UDP-alpha-D-Glc to dTDP/UDP-beta-L-Rha in an NAD(P)H dependent manner. Currently, only biochemical evidence for the function of NRS/ER has been described. In this study, a crystal structure for Arabidopsis thaliana NRS/ER was determined, which is the first report of a eukaryotic rhamnose synthase with both epimerase and reductase activities. NRS/ER functions as a metal ion independent homodimer that forms through hydrophobic interactions via a four-helix bundle. Each monomer exhibits alpha/beta folding that can be divided into two regions, nucleotide cofactor binding domain and sugar substrate binding domain. The affinities of ligands with NRS/ER were measured using isothermal titration calorimetry, which showed that NRS/ER has a preference for dTDP over UDP, while the cofactor binding site has a similar affinity for NADH and NADPH. Structural analysis coupled to site-directed mutagenesis suggested C115 and K183 as the acid/base pair responsible for epimerization, while T113, Y144 and K148 are the conserved residues in reduction. These findings shed light on the molecular mechanism of NRS/ER and were helpful to explore other eukaryotic enzymes involved in L-Rha synthesis. (C) 2015 Elsevier B.V. All rights reserved.