Frener Marina, Micura Ronald
Institute of Organic Chemistry and Center for Molecular Biosciences, University of Innsbruck , 6020 Innsbruck, Austria.
J Am Chem Soc. 2016 Mar 23;138(11):3627-30. doi: 10.1021/jacs.5b11876. Epub 2016 Mar 14.
A pronounced rate differentiation has been found for conformational rearrangements of individual nucleobases that occur during ligand recognition of the preQ1 class-I riboswitch aptamer from Thermoanaerobacter tengcongensis. Rate measurements rely on the 2ApFold approach by analyzing the fluorescence response of riboswitch variants, each with a single, strategically positioned 2-aminopurine nucleobase substitution. Observed rate discrimination between the fastest and the slowest conformational adaption is 22-fold, with the largest rate observed for the rearrangement of a nucleoside directly at the binding site and the smallest rate observed for the 3'-unpaired nucleoside that stacks onto the pseudo-knot-closing Watson-Crick base pair. Our findings provide novel insights into how compact, prefolded RNAs that follow the induced-fit recognition mechanism adapt local structural elements in response to ligand binding on a rather broad time scale and how this process culminates in a structural signal that is responsible for efficient downregulation of ribosomal translation.
已发现来自嗜热栖热放线菌的preQ1 I类核糖开关适体在配体识别过程中发生的单个核碱基构象重排存在明显的速率差异。速率测量依赖于2ApFold方法，通过分析核糖开关变体的荧光响应来进行，每个变体都有一个单一的、位于战略位置的2-氨基嘌呤核碱基取代。观察到的最快和最慢构象适应之间的速率差异为22倍，在结合位点直接观察到的核苷重排速率最大，而在堆积到假结封闭沃森-克里克碱基对上的3'-未配对核苷中观察到的速率最小。我们的研究结果为紧密的、预折叠的RNA如何遵循诱导契合识别机制，在相当宽的时间尺度上响应配体结合而调整局部结构元件，以及这个过程如何最终形成一个负责有效下调核糖体翻译的结构信号，提供了新的见解。
