SUBSTRATE COORDINATION IN RADICAL SAM DEHYDROGENASES

这个子项目是许多研究子项目中利用 资源由NIH/NCRR资助的中心拨款提供。子项目和 调查员(PI)可能从NIH的另一个来源获得了主要资金， 并因此可以在其他清晰的条目中表示。列出的机构是 该中心不一定是调查人员的机构。 自由基SAM脱氢酶利用5‘-脱氧腺苷自由基(5’-da？)通过含有未成对电子的中间体对醇或硫醇进行双电子氧化。那个5英尺长的？通过提取底物上的关键氢原子来启动催化。最近，ATSB是一种自由基SAM酶，催化同源蛋白质上的丝氨酸残基氧化成甲酰甘氨基(FGly)残基，其表征表明它含有三个[4Fe？4S]簇，并提出了一个工作模型，认为其中一个簇与底物接触，通过内球电子转移促进底物自由基中间体的第二电子损失。这项研究的目的是通过模拟底物来验证这一模型，在底物中相关的丝氨基残基被硒半胱氨酸残基取代，并用Se-XAS分析相互作用。

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.