Designed metalloprotein stabilizes a semiquinone radical.
Designed metalloprotein stabilizes a semiquinone radical.
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DOI：
10.1038/nchem.2453
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发表时间：
2016-04
期刊：
影响因子：
21.8
通讯作者：
DeGrado WF
中科院分区：
文献类型：
--
作者：
Ulas G;Lemmin T;Wu Y;Gassner GT;DeGrado WF
酶利用结合能将其底物稳定在高能量状态，否则在环境温度下无法获得。在这里，我们表明，从头设计的Zn（II）金属蛋白稳定的化学反应性有机自由基，否则在水介质中是不稳定的。该蛋白质与3，5-二叔丁基儿茶酚的自由基半醌形式紧密结合并稳定。溶液NMR光谱结合分子动力学模拟表明，基板结合在活性位点口袋中，它是稳定的金属-配体相互作用，以及通过埋葬其疏水基团。光谱化学氧化还原滴定表明，蛋白质通过降低电化学中点电位来稳定半醌，通过儿茶酚的单电子氧化形成半醌约400 mV（9 kcal mol−1）。因此，通过利用其与金属蛋白的结合能，自由基的固有化学性质发生了巨大变化。该模型为设计具有自由基辅因子的酶以应对挑战性化学奠定了基础。
Enzymes use binding energy to stabilize their substrates in high-energy states that are otherwise inaccessible at ambient temperature. Here we show that a de novo designed Zn(ii) metalloprotein stabilizes a chemically reactive organic radical that is otherwise unstable in aqueous media. The protein binds tightly to and stabilizes the radical semiquinone form of 3,5-di-tert-butylcatechol. Solution NMR spectroscopy in conjunction with molecular dynamics simulations show that the substrate binds in the active site pocket where it is stabilized by metal–ligand interactions as well as by burial of its hydrophobic groups. Spectrochemical redox titrations show that the protein stabilized the semiquinone by reducing the electrochemical midpoint potential for its formation via the one-electron oxidation of the catechol by approximately 400 mV (9 kcal mol−1). Therefore, the inherent chemical properties of the radical were changed drastically by harnessing its binding energy to the metalloprotein. This model sets the basis for designed enzymes with radical cofactors to tackle challenging chemistry.