Mg(2+) shifts ligand-mediated folding of a riboswitch from induced-fit to conformational selection.
Mg(2+) shifts ligand-mediated folding of a riboswitch from induced-fit to conformational selection.
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DOI：
10.1021/jacs.5b09740
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发表时间：
2015-11-11
影响因子：
15
通讯作者：
Walter NG
中科院分区：
文献类型：
--
作者：
Suddala KC;Wang J;Hou Q;Walter NG
细菌核糖开关将小分子配体结合偶联到广泛调节基因表达的RNA构象变化，使其成为抗生素干预的潜在靶点。尽管结构的见解，配体介导的核糖开关的折叠机制仍然知之甚少。使用单分子FRET，我们在这里已经调查了H型pseudoknotted preQ1核糖开关的折叠机制依赖于Mg 2+和三个配体的不同的亲和力。我们发现，在没有Mg 2+的情况下，弱结合和强结合的配体通过诱导适合的机制促进假结对接。相比之下，添加低至10 µM的Mg2+通常通过在配体结合之前稳定折叠样构象而使对接朝向构象选择。来自过渡态分析的支持证据进一步强调了诱导拟合期间堆积相互作用以及构象选择期间特定氢键的特别重要性。我们的机械解剖提供了前所未有的深入了解配体和Mg2+介导的RNA折叠之间的复杂协同作用。
Bacterial riboswitches couple small-molecule ligand binding to RNA conformational changes that widely regulate gene expression, rendering them potential targets for antibiotic intervention. Despite structural insights, the ligand mediated folding mechanisms of riboswitches are still poorly understood. Using single molecule FRET, we here have investigated the folding mechanism of an H-type pseudoknotted preQ1 riboswitch in dependence of Mg2+ and three ligands of distinct affinities. We show that in the absence of Mg2+, both weakly and strongly bound ligands promote pseudoknot docking through an induced-fit mechanism. By contrast, addition of as low as 10 µM Mg2+ generally shifts docking toward conformational selection by stabilizing a folded-like conformation prior to ligand binding. Supporting evidence from transition state analysis further highlights the particular importance of stacking interactions during induced-fit, and of specific hydrogen bonds during conformational selection. Our mechanistic dissection provides unprecedented insights into the intricate synergy between ligand- and Mg2+-mediated RNA folding.
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