Mutational alterations of translational coupling in the L11 ribosomal protein operon of Escherichia coli.
Mutational alterations of translational coupling in the L11 ribosomal protein operon of Escherichia coli.
复制标题
大肠杆菌 L11 核糖体蛋白操纵子翻译耦合的突变改变。
DOI：
10.1128/jb.169.8.3495-3507.1987
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发表时间：
1987
影响因子：
3.2
通讯作者：
Nomura,M
中科院分区：
文献类型：
--
作者：
Sor,F;Bolotin-Fukuhara,M;Nomura,M
大肠杆菌中的L11操纵子由编码核糖体蛋白L11和L1的基因组成。众所周知，除非前面的L11顺反子被翻译，否则L1的翻译不会发生，也就是说，两个顺反子是互补偶联的，这是由单个阻遏物L1共同调节两个顺反子翻译的基础。进行了几个突变分析，以确定负责耦合L1翻译与L11翻译的区域。首先，通过定点诱变技术将几个琥珀突变引入L11基因，结果表明，核糖体从L11顺反子末端向下翻译到上游21个核苷酸的位置，但不翻译到上游45个核苷酸的位置，可以启动L11翻译。第二，缺失分析表明，一个区域位于23至20个核苷酸从L11基因的末端参与阻止独立启动从L1翻译。第三，通过筛选被掩蔽的L1起始位点的激活而获得的五种不同的突变被发现聚集在L1的Shine-Dalgarno序列上游的一个小区域中，并且它们都是G到A的转换。这些结果，再加上一些额外的实验与阿托西肽定向诱变，定义的区域参与的耦合，并表明，该地区的一些特殊功能，可能不同于简单的掩蔽的起始位点的碱基配对，是负责翻译耦合。目前的结果还表明，在一级核苷酸序列中可能存在区分独立翻译起始位点与非翻译偶联（即，掩蔽的）起始位点。
The L11 operon in Escherichia coli consists of the genes coding for ribosomal proteins L11 and L1. It is known that translation of L1 does not take place unless the preceding L11 cistron is translated, that is, the two cistrons are translationally coupled, and this is the basis of coregulation of the translation of the two cistrons by a single repressor, L1. Several mutational analyses were carried out to define the region responsible for coupling L1 translation with L11 translation. First, by introducing several amber mutations into the L11 gene by a site-directed mutagenesis technique, it was shown that translation by ribosomes down to a position 21 nucleotides upstream, but not to a position 45 nucleotides upstream, from the end of the L11 cistron allowed the initiation of L11 translation. Second, deletion analysis indicated that a region located 23 to 20 nucleotides from the end of the L11 gene was involved in preventing independent initiation from L1 translation. Third, five different mutations obtained by screening for activation of the masked L1 initiation site were found to be clustered in a small region immediately upstream from the Shine-Dalgarno sequence of L1, and all of them were G-to-A transitions. These results, together with some additional experiments with oligonucleotide-directed mutagenesis, defined the region involved in the coupling and suggest that some special feature of this region, probably different from simple masking of the initiation site by base pairing, is responsible for translational coupling. The present results also suggest that there might be specific differences in the primary nucleotide sequence that distinguish independent translational initiation sites from translationally coupled (i.e., masked) initiation sites.