SUBSTRATE COORDINATION IN RADICAL SAM DEHYDROGENASES

这个子项目是许多研究子项目中的一个 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来源获得了主要资金， 因此可以在其他CRISP条目中表示。所列机构为 研究中心，而研究中心不一定是研究者所在的机构。 自由基SAM脱氢酶利用5 ′-脱氧腺苷自由基（5 ′-dA？）通过含有不成对电子的中间体进行醇或硫醇的双电子氧化。5'-dA？通过夺取底物上的关键氢原子来引发催化。最近，表征AtsB，自由基SAM酶，催化氧化的丝氨酰残基上的同源蛋白质的甲酰甘氨酰（fGly）残基，表明它含有三个[4 Fe？4S]簇，并提出了一个工作模型，该模型建议簇之一与衬底接触结合，以促进通过内层电子转移从衬底自由基中间体损失第二电子。本研究的目的是测试这个模型，通过使用类似的基板，其中相关的丝氨酰基残基被取代的硒半胱氨酰残基和分析的相互作用，硒XAS。

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. Radical SAM dehydrogenases use the oxidizing power of a 5'-deoxyadenosyl radical (5'-dA?) to carry out two-electron oxidations of alcohols or thiols via intermediates containing unpaired electrons. The 5'-dA? initiates catalysis by abstracting a key hydrogen atom on the substrate. Recently, characterization of AtsB, a radical SAM enzyme that catalyzes the oxidation of a seryl residue on a cognate protein to a formylglycyl (fGly) residue, showed that it contained three [4Fe?4S] clusters, and a working model was put forth that suggested that one of the clusters binds in contact with the substrate to facilitate loss of the second electron from a substrate radical intermediate by inner-sphere electron transfer. This study aims to test this model by using an analog of the substrate in which the relevant seryl residue is replaced by a selenocysteinyl residue and analyzing for the interaction by Se XAS.