Dean D, Yates J L, Nomura M
Cell. 1981 May;24(2):413-9. doi: 10.1016/0092-8674(81)90331-7.
A DNA-directed in vitro protein-synthesizing system was used to demonstrate that r protein S7 has the capacity to inhibit the translation of mRNA for the second and third gene products of the str operon (S7 and EF-G) but not for the first gene product (S12). Translation of mRNA of the last gene product in the operon (EF-Tu) is also probably not inhibited by S7. In addition, we localized the target site for S7 repressor action on the polycistronic str mRNA by examining the repressor activity of S7 in vitro using various template DNAs that contain the gene. The target site was found not to include a promoter-proximal portion of the mRNA for S12. To test for regulatory properties of S7 in vivo, we inserted the S7 gene into a plasmid vector containing the ara regulatory elements such that S7 synthesis was placed under ara control. A specific increase in S7 synthesis caused by stimulation in transcription originating from the arabinose promoter decreased the synthetic rate for EF-G but had no effect on S12 or EF-Tu synthesis.
利用一个DNA指导的体外蛋白质合成系统来证明核糖体蛋白S7能够抑制str操纵子中第二和第三个基因产物(S7和EF-G)的mRNA的翻译,但不能抑制第一个基因产物(S12)的mRNA的翻译。操纵子中最后一个基因产物(EF-Tu)的mRNA的翻译可能也不受S7的抑制。此外,我们通过使用含有该基因的各种模板DNA在体外检测S7的阻遏活性,确定了S7阻遏作用在多顺反子str mRNA上的靶位点。发现该靶位点不包括S12的mRNA的启动子近端部分。为了测试S7在体内的调控特性,我们将S7基因插入到一个含有ara调控元件的质粒载体中,使得S7的合成置于ara的控制之下。由阿拉伯糖启动子起始的转录刺激引起的S7合成的特异性增加降低了EF-G的合成速率,但对S12或EF-Tu的合成没有影响。