BASE FLIPPING AND DNA DAMAGE RECOGNITION

DNA碱基切除修复的第一步是由一类 酶，DNA糖基化酶，其促进N-C11- 连接受损或错配碱基与DNA糖的糖基键 磷酸骨架。 DNA暴露于紫外线后，T4 核酸内切酶V通过以下方式启动环丁烷嘧啶二聚体的修复： 特异性糖基化酶和AP裂解酶活性的方法。虽然 催化机制是比较好理解的，事件发生 在糖基键裂解之前的糖基化程度较不明确。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 其决定T4内切核酸酶V结合的特异性。在 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， 通过使用定点突变体阐明。 这些研究将提供 相关的生物化学和结构信息， DNA糖基化酶的一般机制，以及转换的应用 用于DNA修复机制和抑制研究的状态类似物 内切酶

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.