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首页> 外文期刊>Acta crystallographica.Section D. Biological crystallography >Structure of CDP-D-glucose 4,6-dehydratase from Salmonella typhi complexed with CDP-D-xylose
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Structure of CDP-D-glucose 4,6-dehydratase from Salmonella typhi complexed with CDP-D-xylose

机译：6-dehydratase CDP-D-glucose结构4日伤寒沙门氏菌与CDP-D-xylose复杂化

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摘要

Tyvelose is a unique 3,6-dideoxyhexose found in the O antigens of some pathogenic species of Yersinia and Salmonella. It is produced via a complex biochemical pathway that employs CDP-D-glucose as the starting ligand. CDP-D-glucose 4,6-dehydratase catalyzes the first irreversible step in the synthesis of this 3,6-dideoxysugar by converting CDP-D-glucose to CDP-4-keto-6-deoxyglucose via an NAD(+)-dependent intramolecular oxidation-reduction reaction. Here, the cloning, protein purification and X-ray crystallographic analysis of CDP-D-glucose 4,6-dehydratase from Salmonella typhi complexed with the substrate analog CDP-D-xylose are described. Each subunit of the tetrameric enzyme folds into two domains. The N-terminal region contains a Rossmann fold and provides the platform for NAD(H) binding. The C-terminal motif is primarily composed of a-helices and houses the binding pocket for the CDP portion of the CDP-D-xylose ligand. The xylose moiety extends into the active-site cleft that is located between the two domains. Key residues involved in anchoring the sugar group to the protein include Ser134, Tyr159, Asn197 and Arg208. Strikingly, Ser134 O-gamma' and Tyr159 O-eta sit within 2.9 angstrom of the 4'-hydroxyl group of xylose. Additionally, the side chains of Asp135 and Lys136 are located at 3.5 and 3.2 angstrom, respectively, from C-5 of xylose. In the structurally related dTDP-D-glucose 4,6-dehydratase, the Asp/Lys pair is replaced with an Asp/Glu couple. On the basis of this investigation, it can be speculated that Tyr159 serves as the catalytic base to abstract the 4'-hydroxyl proton from the sugar and that Asp135 and Lys136 play critical roles in the subsequent dehydration step that leads to the final product.
机译：6-dideoxyhexose Tyvelose是一个独特的发现一些致病的O抗原的种类就要和沙门氏菌。复杂的生化过程,雇佣了CDP-D-glucose开始配体。CDP-D-glucose 4, 6-dehydratase催化不可逆转的一步合成3, 6-dideoxysugar CDP-D-glucose转化为CDP-4-keto-6-deoxyglucose通过NAD(+)端依赖分子内氧化还原反应。在这里,克隆、蛋白质纯化和x射线晶体分析CDP-D-glucose4, 6-dehydratase从伤寒沙门氏菌复合体与底物模拟CDP-D-xylose描述。折叠成两个领域。包含一个罗斯曼折叠并提供平台NAD (H)绑定。主要是由a-helices和房子的吗绑定口袋的CDP部分CDP-D-xylose配体。的活性部位间隙位置在两个域之间。锚定蛋白包括糖组Ser134、Tyr159 Asn197 Arg208。在2.9 Ser134 O-gamma”和Tyr159 O-eta坐埃4羟基组的木糖。此外,Asp135的侧链Lys136位于3.5和3.2埃,分别从木糖的c - 5。结构相关dTDP-D-glucose4 6-dehydratase Asp /赖氨酸对被替换与一个Asp / Glu夫妇。调查,它可以推测Tyr159作为催化基础抽象4羟基质子从Asp135的糖和在随后和Lys136扮演关键角色脱水步骤,导致最终产品。

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