Riboswitches are conformationally dynamic RNAs that regulate gene expression by binding specific small molecules. ZTP riboswitches bind the purine‐biosynthetic intermediate 5‐aminoimidazole‐4‐carboxamide riboside 5′‐monophosphate (ZMP) and its triphosphorylated form (ZTP). Ligand binding to this riboswitch ultimately upregulates genes involved in folate and purine metabolism. Using an X‐ray free‐electron laser (XFEL), the room‐temperature structure of the Fusobacterium ulcerans ZTP riboswitch bound to ZMP has now been determined at 4.1 Å resolution. This model, which was refined against a data set from ∼750 diffraction images (each from a single crystal), was found to be consistent with that previously obtained from data collected at 100 K using conventional synchrotron X‐radiation. These experiments demonstrate the feasibility of time‐resolved XFEL experiments to understand how the ZTP riboswitch accommodates cognate ligand binding.

中文翻译：

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使用X射线自由电子激光对溃疡分枝杆菌ZTP核糖开关的共晶体结构。

核糖开关是通过结合特定的小分子来调节基因表达的构象动态RNA。ZTP核糖开关结合嘌呤生物合成中间体5-氨基咪唑-4-羧酰胺核糖5'-单磷酸酯（ZMP）及其三磷酸化形式（ZTP）。与该核糖开关结合的配体最终上调了参与叶酸和嘌呤代谢的基因。使用X射线自由电子激光（XFEL），溃疡镰刀菌的室温结构现已确定与ZMP结合的ZTP核糖开关的分辨率为4.1Å。该模型针对约750个衍射图像（每个晶体均来自单晶）的数据集进行了精炼，发现该模型与先前使用常规同步辐射X射线从100 K收集的数据中获得的模型一致。这些实验证明了时间分辨XFEL实验的可行性，以了解ZTP核糖开关如何适应同源配体结合。