Structural basis of amino acid surveillance by higher-order tRNA-mRNA interactions
Structural basis of amino acid surveillance by higher-order tRNA-mRNA interactions
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DOI：
10.1038/s41594-019-0326-7
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发表时间：
2019-12-01
影响因子：
16.8
通讯作者：
Zhang, Jinwei
中科院分区：
文献类型：
--
作者：
Li, Shuang;Su, Zhaoming;Zhang, Jinwei
革兰氏阳性菌中的氨基酸可用性由 T 盒核糖开关监测。 T-box直接结合tRNA，评估其氨酰化状态，并调节下游基因的转录或翻译以维持营养稳态。在这里，我们报告了嗜地芽孢杆菌和枯草芽孢杆菌 T-box-tRNA 复合物的共晶和冷冻电镜结构，详细描述了它们的多价、精确选择性的相互作用。 T-box 形成一个 U 形分子虎钳，夹住 tRNA，使用精心设计的“鉴别器”结构捕获其 3' 末端，并使用由摆动碱基对形成的空间过滤器询问其氨酰化状态。在没有氨酰化的情况下，T 盒抓住 tRNA 并形成连续堆叠的中央脊柱，允许转录通读或翻译启动。模拟的氨酰会破坏 tRNA-T-box 堆积，切断中央脊柱并阻断基因表达。我们的数据建立了 tRNA 氨基酸传感和 T-box 核糖开关基因调控的通用机制，并举例说明了高阶 RNA-RNA 相互作用如何实现多价性和特异性。
Amino acid availability in Gram-positive bacteria is monitored by T-box riboswitches. T-boxes directly bind tRNAs, assess their aminoacylation state, and regulate the transcription or translation of downstream genes to maintain nutritional homeostasis. Here, we report cocrystal and cryo-EM structures of Geobacillus kaustophilus and Bacillus subtilis T-box-tRNA complexes, detailing their multivalent, exquisitely selective interactions. The T-box forms a U-shaped molecular vise that clamps the tRNA, captures its 3' end using an elaborate 'discriminator' structure, and interrogates its aminoacylation state using a steric filter fashioned from a wobble base pair. In the absence of aminoacylation, T-boxes clutch tRNAs and form a continuously stacked central spine, permitting transcriptional readthrough or translation initiation. A modeled aminoacyl disrupts tRNA-T-box stacking, severing the central spine and blocking gene expression. Our data establish a universal mechanism of amino acid sensing on tRNAs and gene regulation by T-box riboswitches and exemplify how higher-order RNA-RNA interactions achieve multivalency and specificity.