T-box riboregulators are a class of cis-regulatory RNAs that govern the bacterial response to amino acid starvation by binding, decoding and reading the aminoacylation status of specific transfer RNAs. Here we provide a high-resolution crystal structure of a full-length T-box from Mycobacterium tuberculosis that explains tRNA decoding and aminoacylation sensing by this riboregulator. Overall, the T-box consists of decoding and aminoacylation sensing modules bridged by a rigid pseudoknot structure formed by the mid-region domains. Stem-I and the Stem-II S-turn assemble a claw-like decoding module, while the antiterminator, Stem-III, and the adjacent linker form a tightly interwoven aminoacylation sensing module. The uncharged tRNA is selectively recognized by an unexpected set of favorable contacts from the linker region in the aminoacylation sensing module. A complex structure with a charged tRNA mimic shows that the extra moiety dislodges the linker, which is indicative of the possible chain of events that lead to alternative base-pairing and altered expression output.

中文翻译：

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T-box核糖调节剂对tRNA解码和氨酰化传感的结构基础。

T-box riboregulators 是一类顺式调节 RNA，通过结合、解码和读取特定转移 RNA 的氨酰化状态来控制细菌对氨基酸饥饿的反应。在这里，我们提供了来自结核分枝杆菌的全长 T 盒的高分辨率晶体结构，它解释了这种核糖调节剂的 tRNA 解码和氨酰化传感。总体而言，T-box 由解码和氨酰化传感模块组成，这些模块由中间区域形成的刚性假结结构桥接。Stem-I 和 Stem-II S-turn 组装成爪状解码模块，而反终止子 Stem-III 和相邻的接头形成紧密交织的氨酰化传感模块。不带电荷的 tRNA 被来自氨酰化传感模块中接头区域的一组意想不到的有利接触选择性地识别。带有带电 tRNA 模拟物的复杂结构表明，额外的部分会移动接头，这表明可能导致替代碱基配对和改变表达输出的事件链。