Kang C W, Cantor C R
J Mol Biol. 1985 Jan 20;181(2):241-51. doi: 10.1016/0022-2836(85)90088-9.
Digestion with ribonuclease T2 has been used to study the size of poly(U) protected by ribosome binding. Several different preparations of ribosomes all appear to cover 49 nucleotides of message; however, there are two partially accessible internal nuclease cleavage sites, which yield, ultimately, fragments 20, 16 and 13 nucleotides in length. Curiously, the site between fragments of length 20 and 16 is accessible to RNase T2 but not to the several much smaller RNases. Arguments based on the quantitative pattern of cleavage and comparisons with previous studies lead to the conclusion that the 20-mer is the 5' fragment, while 13-mer (which is lost the moment it is cleaved from the 16-mer) is the 3' fragment. Both ribosome-bound tRNAs appear to contact only the 16-mer. The presence of the two internal cleavage sites fits nicely with recent electron microscopic data suggesting that mRNA forms a loop around the 30 S subunit.
用核糖核酸酶T2消化已被用于研究核糖体结合所保护的聚尿苷酸（poly(U)）的大小。几种不同的核糖体制剂似乎都覆盖了49个核苷酸的信使核糖核酸（mRNA）；然而，有两个部分可及的内部核酸酶切割位点，最终产生长度为20、16和13个核苷酸的片段。奇怪的是，长度为20和16的片段之间的位点可被核糖核酸酶T2作用，但不能被几种小得多的核糖核酸酶作用。基于切割的定量模式以及与先前研究的比较得出的结论是，20聚体是5'片段，而13聚体（从16聚体切割下来后立即消失）是3'片段。两个与核糖体结合的转运核糖核酸（tRNA）似乎都只与16聚体接触。这两个内部切割位点的存在与最近的电子显微镜数据非常吻合，这些数据表明mRNA在30 S亚基周围形成一个环。
