DNA SEARCH AND BASE FLIPPING MECHANISMS OF DNA GLYCOSYLASE, MUTM

该子项目是利用 由NIH/NCRR资助的中心赠款提供的资源。子项目和 研究者（PI）可能从另一个NIH来源获得主要资金， 因此可以在其他CRISP条目中表示。列出的机构是 中心，不一定是研究者的机构。 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，目前还没有很好的理解，蛋白质是否积极促进碱基挤出目前仍存在争议。 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. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. 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.