Heteronuclear NMR and crystallographic studies of wild-type and H187Q Escherichia coli uracil DNA glycosylase:: Electrophilic catalysis of uracil expulsion by a neutral histidine 187
Heteronuclear NMR and crystallographic studies of wild-type and H187Q Escherichia coli uracil DNA glycosylase:: Electrophilic catalysis of uracil expulsion by a neutral histidine 187
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DOI：
10.1021/bi9910880
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发表时间：
1999-09-14
期刊：
影响因子：
2.9
通讯作者：
Stivers, JT
中科院分区：
文献类型：
--
作者：
Drohat, AC;Xiao, GY;Stivers, JT
用X射线晶体学和核磁共振谱研究了大肠杆菌尿嘧啶DNA糖基化酶（UDG）催化反应中的一般酸His 187的性质。H187 Q UDG及其与尿嘧啶的复合物的晶体结构已分别在1.40和1.60埃分辨率下解析。其结构与野生型酶基本相同，只是Gln 187的侧链偏离尿嘧啶碱基，不能与尿嘧啶O2相互作用。这一结果为H187 Q和H187 A酶相似的动力学性质提供了结构基础。His 187的电离状态直接用针对组氨酸环自旋系统优化的H-1-N-15 NMR实验来解决，其确定His 187在酶的催化活性状态下是中性的（pK（a））。
The nature of the putative general acid His187 in the reaction catalyzed by Escherichia coli uracil DNA glycosylase (UDG) was investigated using X-ray crystallography and NMR spectroscopy. The crystal structures of H187Q UDG, and its complex with uracil, have been solved at 1.40 and 1.60 Angstrom resolution, respectively. The structures are essentially identical to those of the wild-type enzyme, except that the side chain of Gln187 is turned away from the uracil base and cannot interact with uracil O2. This result provides a structural basis for the similar kinetic properties of the H187Q and H187A enzymes. The ionization state of His187 was directly addressed with H-1-N-15 NMR experiments optimized for histidine ring spin systems, which established that His 187 is neutral in the catalytically active state of the enzyme (pK(a)