Radical SAM Enzymes: Molecular Mechanisms of Radical Initiation

自由基SAM是已知的最大的酶超家族之一，其成员催化一种 在生活的各个领域都有着惊人的多样性反应。自由基SAM酶参与了 合成必需的辅因子和抗生素，修复DNA损伤，组装复合物 生物金属簇，以及许多其他反应。自由基SAM酶在人类中的存在 以及在有益和致病微生物中， 基本属性和机制。拟议的研究将发展一个批判性的理解， 自由基SAM机制，特别是自由基引发过程共同的所有酶在这个大的 多样的超家族。研究工作将集中在捕获自由基中间体使用快速冷冻- 淬火、低温还原、退火和光解方法。这些中间体将被 其特征在于使用光谱方法，例如电子顺磁共振和电子- 核双共振和结构方法，如X射线晶体学。计算 研究将提供对稳定性/反应性和反应途径的深入了解。大部分工作将建立在 关于最近发现的一种新的有机金属中间体， 铁硫簇的一个碳和腺苷部分的一个碳，这是一种让人想起辅酶B12的结构。 研究结果将有助于理解生物学中这种基本的、普遍存在的反应， 有机金属化学的惊人参与。

Radical SAM is one of the largest enzyme superfamilies known, with its members catalyzing a remarkable diversity of reactions in all domains of life. Radical SAM enzymes are involved in the synthesis of essential cofactors and antibiotics, repair of DNA damage, and the assembly of complex biological metal clusters, among many other reactions. The presence of radical SAM enzymes in humans as well as in both beneficial and pathogenic microbes lends high significance to understanding their fundamental properties and mechanisms. The proposed research will develop a critical understanding of radical SAM mechanisms, in particular the radical initiation process common to all enzymes in this large and diverse superfamily. Research efforts will focus on trapping radical intermediates using rapid freeze- quench, cryoreduction, annealing, and photolysis approaches. These intermediates will then be characterized by using spectroscopic approaches such as electron paramagnetic resonance and electron- nuclear double resonance, and structural approaches such as X-ray crystallography. Computational studies will provide insights into stability/reactivity and reaction pathways. Much of the work will build on the recent discovery of a novel organometallic intermediate containing a direct bond between an iron of the iron-sulfur cluster and a carbon of an adenosyl moiety, a structure reminiscent of coenzyme B12. The results will provide an understanding of this fundamental and ubiquitous reaction in biology, and its surprising involvement of organometallic chemistry.