Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, MD, 20892, USA.
Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, MD, 20892, USA.
Nat Commun. 2023 Sep 6;14(1):5438. doi: 10.1038/s41467-023-41155-3.
T-box riboswitches are multi-domain noncoding RNAs that surveil individual amino acid availabilities in most Gram-positive bacteria. T-boxes directly bind specific tRNAs, query their aminoacylation status to detect starvation, and feedback control the transcription or translation of downstream amino-acid metabolic genes. Most T-boxes rapidly recruit their cognate tRNA ligands through an intricate three-way stem I-stem II-tRNA interaction, whose establishment is not understood. Using single-molecule FRET, SAXS, and time-resolved fluorescence, we find that the free T-box RNA assumes a broad distribution of open, semi-open, and closed conformations that only slowly interconvert. tRNA directly binds all three conformers with distinct kinetics, triggers nearly instantaneous collapses of the open conformations, and returns the T-box RNA to their pre-binding conformations upon dissociation. This scissors-like dynamic behavior is enabled by a hinge-like pseudoknot domain which poises the T-box for rapid tRNA-induced domain closure. This study reveals tRNA-chaperoned folding of flexible, multi-domain mRNAs through a Venus flytrap-like mechanism.
T 盒核糖体开关是多结构域非编码 RNA，可监测大多数革兰氏阳性菌中单个氨基酸的可用性。T 盒可直接结合特定的 tRNA，查询其氨酰化状态以检测饥饿，并反馈控制下游氨基酸代谢基因的转录或翻译。大多数 T 盒通过复杂的三链茎 I-茎 II-tRNA 相互作用快速募集其同源 tRNA 配体，其建立机制尚不清楚。我们使用单分子 FRET、SAXS 和时间分辨荧光发现，游离 T 盒 RNA 呈现出开放、半开放和闭合构象的广泛分布，这些构象仅缓慢相互转化。tRNA 以不同的动力学与所有三种构象直接结合，触发开放构象的几乎瞬时坍塌，并在解离时将 T 盒 RNA 返回到其预结合构象。这种类似剪刀的动态行为是由铰链样假结结构域实现的，该结构域使 T 盒能够快速进行 tRNA 诱导的结构域关闭。这项研究揭示了通过 Venus flytrap 样机制对灵活的多结构域 mRNA 进行 tRNA 介导的折叠。
