目的· 研究SUMO 化修饰对胸腺嘧啶DNA 糖基化酶（thymine DNA glycosylase，TDG）蛋白的结构、稳定性及活性的影响。
方法· 建立体外表达纯化体系，获取可用于晶体筛选及活性检测的SUMO-1-TDG 蛋白。通过晶体筛选、衍射数据收集及结构解析，
分析SUMO-1-TDG 的分子结构。利用蛋白热稳定性实验检测在SUMO 化修饰前后TDG 稳定性的变化。建立TDG 活性测试体系，探
讨SUMO 化修饰对TDG 活性产生的影响。结果· 通过结构解析得到SUMO-1-TDG 分子结构。稳定性、活性实验检测发现TDG 蛋白
熔解温度（Tm）值提高约16℃，催化活性提升约9.70 %。结论· SUMO-1 分子结合TDG 对其进行修饰使得结合位点附近氨基酸形成
分子间相互作用，并进一步参与调控TDG 蛋白的稳定性及催化活性。

Objective · To study the effect of sumoylation on the structure, stability and activity of human thymine DNA glycosylase (TDG).
Methods · Expression and purification systems were established for obtaining SUMO-1-TDG protein with high purity which can be used for crystal
screening and activity detection. Structure of SUMO-1-TDG was solved after crystal screening, diffraction data collection and structure analysis. The
change of TDG stability led by sumoylation was detected through a protein thermal shift assay. In addition, an activity assay was applied to investigate the
effect of sumoylation on the activity of TDG. Results · A high-resolution structure of SUMO-1-TDG which could clearly describe the interaction between
TDG and SUMO-1 was solved. The melting temperature (Tm) value of SUMO-1-TDG increased by about 16 ℃ and the catalytic activity increased by 9.70%,
comparing with TDG protein. Conclusion · SUMO-1 binds to TDG to modify the intermolecular interaction of amino acids near the binding site, and
further participates in the regulation of the stability and catalytic activity of TDG protein.