RatA (YfjG), an Escherichia coli toxin, inhibits 70S ribosome association to block translation initiation.
RatA (YfjG), an Escherichia coli toxin, inhibits 70S ribosome association to block translation initiation.
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DOI：
10.1111/j.1365-2958.2010.07506.x
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发表时间：
2011-03
影响因子：
3.6
通讯作者：
Inouye M
中科院分区：
文献类型：
--
作者：
Zhang Y;Inouye M
RatA (YfjG) 是由大肠杆菌基因组上的ratA-ratB (yfjG-yfjF) 操纵子编码的毒素。 RatA的诱导导致蛋白质合成受到抑制，而DNA和RNA合成不受影响。根据体内引物延伸实验和 Northern blotting 分析判断，mRNA 的稳定性也没有变化。过表达 RatA 的细胞的核糖体谱显示，70S 核糖体以及多核糖体显着减少，同时 50S 和 30S 亚基增加。将纯化的 RatA 添加到无细胞系统中，即使存在 6 mM Mg2+，也能抑制 70S 核糖体的形成。 RatA 与 50S 亚基特异性相关，表明它与 50S 亚基结合以阻断其与 30S 亚基的结合，从而抑制 70S 核糖体的形成。然而，RatA 不会引起 70S 核糖体解离，其抗缔合活性被巴龙霉素阻断，巴龙霉素是 IF3 的抑制剂，是一种重要的起始因子，与 RatA 具有 21% 的序列同源性。在这里，我们证明 RatA 是一种新的大肠杆菌毒素，它可以有效地阻断翻译起始步骤。我们建议将这种以前未知功能的毒素重命名为RatA（核糖体联合毒素A）。
RatA (YfjG) is a toxin encoded by the ratA-ratB (yfjG-yfjF) operon on the Escherichia coli genome. Induction of RatA led to the inhibition of protein synthesis, while DNA and RNA synthesis was not affected. The stability of mRNAs was also unchanged as judged by in vivo primer extension experiments and by Northern blotting analysis. The ribosome profile of the cells overexpressing RatA showed that 70S ribosomes as well as polysomes significantly decreased with concomitant increase of 50S and 30S subunits. The addition of purified RatA to a cell-free system inhibited the formation of 70S ribosomes even in the presence of 6 mM Mg2+. RatA was specifically associated with 50S subunits, indicating that it binds to 50S subunits to block its association with 30S subunits leading to the inhibition of formation of 70S ribosomes. However, RatA did not cause dissociation of 70S ribosomes and its anti-association activity was blocked by paromomycin, an inhibitor for IF3, an essential initiation factor, having 21% sequence homology with RatA. Here we demonstrate that RatA is a new E. coli toxin, which effectively blocks the translation initiation step. We propose that this toxin of previously unknown function be renamed as RatA (Ribosome association toxin A).
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