The Crystal Structures of the Open and Catalytically Competent Closed Conformation of Escherichia coli Glycogen Synthase
The Crystal Structures of the Open and Catalytically Competent Closed Conformation of Escherichia coli Glycogen Synthase
复制标题
DOI：
10.1074/jbc.m809804200
复制
发表时间：
2009-06-26
影响因子：
4.8
通讯作者：
Geiger, James H.
中科院分区：
文献类型：
--
作者：
Sheng, Fang;Jia, Xiaofei;Geiger, James H.
大肠杆菌糖原合酶（EcGS，EC 2.4.1.21）是一种保留糖基转移酶（GT），其将葡萄糖从腺苷二磷酸葡萄糖转移至葡聚糖链受体，并保留异头碳处的构型。EcGS属于GT-B结构超家族。在这里，我们报告了几个EcGS的X射线结构，这些酶的结构和功能，一起揭示了相当大的光。结合ADP和葡萄糖的野生型酶的结构揭示了15.2度的整体结构域-结构域闭合，并首次提供了糖原合酶的催化活性的闭合构象的结构。His-161、Arg-300和Lys-305的主链羰基由结构表明在转糖基化中充当关键催化残基。Glu-377，以前被认为是催化剂，发现在葡萄糖的α-面，并在活性位点发挥静电作用，并作为葡萄糖环定位器。这也与EcGS（E377 A）-ADP-HEPPSO复合物的结构一致，其中葡萄糖部分在活性位点中不存在或无序。
Escherichia coli glycogen synthase (EcGS, EC 2.4.1.21) is a retaining glycosyltransferase (GT) that transfers glucose from adenosine diphosphate glucose to a glucan chain acceptor with retention of configuration at the anomeric carbon. EcGS belongs to the GT-B structural superfamily. Here we report several EcGS x-ray structures that together shed considerable light on the structure and function of these enzymes. The structure of the wild-type enzyme bound to ADP and glucose revealed a 15.2 degrees overall domain-domain closure and provided for the first time the structure of the catalytically active, closed conformation of a glycogen synthase. The main chain carbonyl group of His-161, Arg-300, and Lys-305 are suggested by the structure to act as critical catalytic residues in the transglycosylation. Glu-377, previously thought to be catalytic is found on the alpha-face of the glucose and plays an electrostatic role in the active site and as a glucose ring locator. This is also consistent with the structure of the EcGS(E377A)-ADP-HEPPSO complex where the glucose moiety is either absent or disordered in the active site.