Crucial Roles of Two Hydrated Mg2+ Ions in Reaction Catalysis of the Pistol Ribozyme
Crucial Roles of Two Hydrated Mg2+ Ions in Reaction Catalysis of the Pistol Ribozyme
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两个水合 Mg2 离子在手枪核酶反应催化中的关键作用
DOI：
10.1002/anie.201912522
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发表时间：
2020-01-09
影响因子：
16.6
通讯作者：
Micura，Ronald
中科院分区：
文献类型：
--
作者：
Teplova，Marianna;Falschlunger，Christoph;Micura，Ronald
手枪核酶是一类新型的小分子自切割RNA。晶体结构已被解决，提供了三维快照沿着手枪磷酸二酯裂解的反应坐标，对应于预催化状态，过渡态的钒酸盐模拟物，和产品。这些结果导致了所提出的潜在化学机制。重要的是，水合Mg 2+离子在所有三种状态下都保持与G33的N7内球配位，并且与其在一般酸碱催化（δ和β催化）中作为酸的可能作用一致。引人注目的是，新结构揭示了第二个水合Mg 2+离子，该离子在预裂解状态下从其结合位点接近易分裂的磷酸盐，以在环磷酸盐产物中形成水介导的氢键。第二个Mg 2+离子的主要作用似乎是稳定的产品构象。这项研究提供了一个机制的理解核酶催化的主链裂解。
Pistol ribozymes constitute a new class of small self‐cleaving RNAs. Crystal structures have been solved, providing three‐dimensional snapshots along the reaction coordinate of pistol phosphodiester cleavage, corresponding to the pre‐catalytic state, a vanadate mimic of the transition state, and the product. The results led to the proposed underlying chemical mechanism. Importantly, a hydrated Mg2+ion remains innersphere‐coordinated to N7 of G33 in all three states, and is consistent with its likely role as acid in general acid base catalysis (δ and β catalysis). Strikingly, the new structures shed light on a second hydrated Mg2+ion that approaches the scissile phosphate from its binding site in the pre‐cleavage state to reach out for water‐mediated hydrogen bonding in the cyclophosphate product. The major role of the second Mg2+ion appears to be the stabilization of product conformation. This study delivers a mechanistic understanding of ribozyme‐catalyzed backbone cleavage.