Himeno H, Sato M, Tadaki T, Fukushima M, Ushida C, Muto A
Department of Biology, Faculty of Science, Hirosaki University, Japan.
J Mol Biol. 1997 May 23;268(5):803-8. doi: 10.1006/jmbi.1997.1011.
10Sa RNA is a bacterial small stable RNA, in which the 5' and 3'-terminal sequences can be folded into a tRNA-like secondary structure which can be aminoacylated with alanine. It was found that Escherichia coli 10Sa RNA facilitated the incorporation of alanine, tyrosine, aspartic acid and glutamic acid, but not valine, isoleucine, serine or arginine, into the growing polypeptide in vitro, depending on poly (U)-directed poly-phenylalanine synthesis. This result indicates that 10Sa RNA functions as an mRNA for the tag-peptide which has been found to be attached to the C termini of truncated polypeptides synthesized in vivo. Aminoacylation with alanine was required for tag-specific amino acid incorporation and for efficient association of 10Sa RNA with the ribosome, indicating that 10Sa RNA also functions as an alanine tRNA in the tag-peptide synthesis. The dual function of 10Sa RNA both as an mRNA and as a tRNA in vitro strongly supports the trans translation hypothesis.
10Sa RNA是一种细菌小稳定RNA，其5'和3'末端序列可折叠成类似tRNA的二级结构，该结构可被丙氨酸氨酰化。研究发现，大肠杆菌10Sa RNA在体外依赖于聚（U）指导的聚苯丙氨酸合成，促进丙氨酸、酪氨酸、天冬氨酸和谷氨酸掺入正在生长的多肽中，但缬氨酸、异亮氨酸、丝氨酸或精氨酸则不能。这一结果表明，10Sa RNA作为已发现附着于体内合成的截短多肽C末端的标签肽的信使RNA发挥作用。标签特异性氨基酸掺入以及10Sa RNA与核糖体的有效结合需要丙氨酸氨酰化，这表明10Sa RNA在标签肽合成中也作为丙氨酸tRNA发挥作用。10Sa RNA在体外作为信使RNA和tRNA的双重功能有力地支持了反式翻译假说。
