DNA SEARCH AND BASE FLIPPING MECHANISMS OF DNA GLYCOSYLASE, MUTM

这个子项目是许多利用资源的研究子项目之一 由NIH/NCRR资助的中心拨款提供。子项目的主要支持 而子项目的主要调查员可能是由其他来源提供的， 包括其它NIH来源。 列出的子项目总成本可能 代表子项目使用的中心基础设施的估计数量， 而不是由NCRR赠款提供给子项目或子项目工作人员的直接资金。 MutM是一种细菌DNA糖基化酶，其特异性识别氧化损伤的DNA碱基并启动碱基切除修复途径。鉴于病变碱基（8-氧代鸟嘌呤）和正常DNA碱基（鸟嘌呤）的细微构象差异，以及病变的稀缺性，一个根本问题出现了：MutM如何在庞大的基因组中定位罕见的病变位点？此外，碱基翻转是DNA糖基化酶催化的一个重要步骤，目前还不清楚，蛋白质是否积极促进碱基挤出目前存在争议。使用二硫键交联策略，我们共价捕获通常短暂的中间体在搜索过程中MutM的病变在核碱基挤出。这些中间体不仅阐明了损伤识别和催化的机制，而且为我们的基础挤出途径的计算研究提供了有价值的起点。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. MutM is a bacterial DNA glycosylase that specifically recognizes oxidatively damaged DNA bases and initiates the base excision repair pathway. Given the subtle conformational differences in the lesion base, 8-oxoguanine, and normal DNA base, guanine, and the scarcity of the lesions, a fundamental question arises: how does MutM locate the rare lesion sites among the vast genome? In addition, base flipping, an essential step for DNA glycosylase catalysis, is not well understood, and whether protein is actively promoting base extrusion is currently in debate. Using the disulfide crosslinking strategy, we have covalently trapped ordinarily transient intermediates during the search by MutM for lesions during nucleobase extrusion. These intermediates not only shed light on the mechanism of lesion recognition and catalysis, but have also provided valuable starting points for our computational studies of the base extrusion pathway.