Frontier Institute for Biomolecular Engineering Research (FIBER), Konan University, 7-1-20 Minatojima-minamimachi, Kobe 650-0047 (Japan).
Angew Chem Int Ed Engl. 2015 Jan 12;54(3):905-9. doi: 10.1002/anie.201407385. Epub 2014 Dec 2.
Riboswitch-mediated control of gene expression depends on ligand binding properties (kinetics and affinity) of its aptamer domain. A detailed analysis of interior regions of the aptamer, which affect the ligand binding properties, is important for both understanding natural riboswitch functions and for enabling rational design of tuneable artificial riboswitches. Kinetic analyses of binding reaction between flavin mononucleotide (FMN) and several natural and mutant aptamer domains of FMN-specific riboswitches were performed. The strong dependence of the dissociation rate (52.6-fold) and affinity (100-fold) on the identities of base pairs in the aptamer stem suggested that the stem region, which is conserved in length but variable in base-pair composition and context, is the tuning region of the FMN-specific aptamer. Synthetic riboswitches were constructed based on the same aptamer domain by rationally modifying the tuning regions. The observed 9.31-fold difference in the half-maximal effective concentration (EC50) corresponded to a 11.6-fold difference in the dissociation constant (K(D)) of the aptamer domains and suggested that the gene expression can be controlled by rationally adjusting the tuning regions.
核糖开关介导的基因表达调控取决于其适体结构域与配体结合的性质（动力学和亲和力）。深入分析影响配体结合性质的适体内部结构域，对于理解天然核糖开关的功能以及实现可调谐人工核糖开关的合理设计都非常重要。对黄素单核苷酸（FMN）与几种 FMN 特异性核糖开关的天然和突变适体结构域之间的结合反应进行了动力学分析。解离速率（52.6 倍）和亲和力（100 倍）强烈依赖于适体茎中的碱基对的特性表明，该茎区域在长度上是保守的，但在碱基对组成和上下文上是可变的，是 FMN 特异性适体的调谐区域。通过合理修饰调谐区域，基于相同的适体结构域构建了合成的核糖开关。观察到的半最大有效浓度（EC50）差异为 9.31 倍，相应的适体结构域的解离常数（K(D)）差异为 11.6 倍，这表明可以通过合理调节调谐区域来控制基因表达。
