BASE FLIPPING AND DNA DAMAGE RECOGNITION

DNA碱基切除修复的第一步是由一类 酶，DNA糖基酶，促进N-C11- 将受损或错配的碱基连接到DNA糖上的糖基键 磷酸盐骨架。DNA暴露于紫外光后，T4 核酸内切酶V通过以下途径启动环丁烷嘧啶二聚体的修复 测定特定糖基酶和AP裂解酶的活性。尽管 催化机制是比较清楚的，事件发生 在糖键断裂之前，糖基键的定义不是很清楚。vbl.使用 假定的过渡态和底物类似物，我们建议检查 DNA和反应中间体的结构特征 它们决定了T4核酸内切酶V结合的特异性。在……里面 此外，所需的蛋白质结构的关键特征 对于差异结合，碱基翻转和催化将是 通过使用定点突变体来阐明。这些研究将提供 有关生物化学和结构方面的信息 DNA糖基酶的一般机制及其转换的应用 DNA修复的机制和抑制研究的状态类似物 酵素。

The first step in DNA base excision repair is catalyzed by a class of enzymes, DNA glycosylases, which promote the scission of the N-C1 1 - glycosyl bond linking a damaged or mismatched base to the DNA sugar phosphate backbone. Following exposure of DNA to ultraviolet light, T4 endonuclease V initiates the repair of cyclobutane pyrimidine dimers by way of specific glycosylase and AP lyase activities. Although the catalytic mechanism is relatively well-understood, the events occurring prior to the cleavage of the glycosyl bond are less well defined. Using putative transition state and substrate analogs, we propose to examine the structural features of both the DNA and the reaction intermediates which determine the specificity of T4 endonuclease V binding. In addition, the key features of the protein architecture that are required for differential binding, base flipping, and catalysis will be elucidated by use o site-directed mutants. These studies will provide pertinent biochemical and structural information regarding the generalized mechanisms of DNA glycosylases, and the use o transition state analogs for mechanistic and inhibition studies of DNA repair enzymes.