Supplementary Material for: Subunit Composition of Ribosome in the <b><i>yqgF</i></b> Mutant Is Deficient in pre-16S rRNA Processing of <b><i>Escherichia coli</i></b>

<i>Escherichia coli</i> 16S, 23S, and 5S ribosomal RNAs (rRNAs) are transcribed as a single primary transcript, which is subsequently processed into mature rRNAs by several RNases. Three RNases (RNase III, RNase E, and RNase G) were reported to function in processing the 5′-leader of precursor 16S rRNA (pre-16S rRNA). Previously, we showed that a novel essential YqgF is involved in that processing. Here we investigated the ribosome subunits of the <i>yqgF</i>^ts mutant by LC-MS/MS. The mutant ribosome had decreased copy numbers of ribosome protein S1, suggesting that the <i>yqgF</i> gene enables incorporation of ribosomal protein S1 into ribosome by processing of the 5′-end of pre-16S rRNA. The ribosome protein S1 is essential for translation in <i>E. coli</i>; therefore, our results suggest that YqgF converts the inactive form of newly synthesized ribosome into the active form at the final step of ribosome assembly.大肠杆菌（Escherichia coli）的16S、23S及5S核糖体RNA（rRNA）首先以单一条初级转录本的形式转录，随后经多种核糖核酸酶加工为成熟rRNA。已有研究显示，三类核糖核酸酶——RNase III、RNase E与RNase G——参与前体16S rRNA（pre-16S rRNA）的5′先导序列加工。本团队此前的研究证实，一种全新的必需基因YqgF同样参与该加工过程。本研究通过液相色谱-串联质谱（LC-MS/MS）分析了yqgF^ts温度敏感突变体的核糖体亚基组成，发现该突变体的核糖体中核糖体蛋白S1的拷贝数显著降低。上述结果提示，yqgF基因可通过加工前体16S rRNA的5′端，介导核糖体蛋白S1整合进入核糖体。核糖体蛋白S1是大肠杆菌翻译过程的必需因子，因此本研究结果表明，YqgF可在核糖体组装的最终步骤中，将新合成的无活性核糖体转化为具有翻译活性的成熟核糖体。