Ribosomal stalling is used to regulate gene expression and can occur in a species-specific manner. Stalling during translation of the MifM leader peptide regulates expression of the downstream membrane protein biogenesis factor YidC2 (YqjG) in Bacillus subtilis, but not in Escherichia coli. In the absence of structures of Gram-positive bacterial ribosomes, a molecular basis for species-specific stalling has remained unclear. Here we present the structure of a Gram-positive B. subtilis MifM-stalled 70S ribosome at 3.5-3.9 Å, revealing a network of interactions between MifM and the ribosomal tunnel, which stabilize a non-productive conformation of the PTC that prevents aminoacyl-tRNA accommodation and thereby induces translational arrest. Complementary genetic analyses identify a single amino acid within ribosomal protein L22 that dictates the species specificity of the stalling event. Such insights expand our understanding of how the synergism between the ribosome and the nascent chain is utilized to modulate the translatome in a species-specific manner.

中文翻译：

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枯草芽孢杆菌70S核糖体的结构揭示了物种特异性失速的基础。

核糖体失速用于调节基因表达，并且可以以物种特异性的方式发生。MifM前导肽翻译过程中的停转调节了枯草芽孢杆菌而不是大肠杆菌中下游膜蛋白生物发生因子YidC2（YqjG）的表达。在缺乏革兰氏阳性细菌核糖体的结构的情况下，物种特异性停滞的分子基础仍然不清楚。在这里，我们介绍了革兰氏阳性枯草芽孢杆菌MifM老化的70S核糖体在3.5-3.9Å的结构，揭示了MifM与核糖体通道之间的相互作用网络，该网络稳定了PTC的非生产性构象，从而防止了氨酰基- tRNA调节，从而诱导翻译停滞。补充遗传分析确定了核糖体蛋白L22中的单个氨基酸，该氨基酸决定了失速事件的物种特异性。这些见解扩大了我们对如何利用核糖体和新生链之间的协同作用以物种特异性方式调节转座子的理解。