Davis F C, Mullersman R W
Biochemistry. 1981 Jun 9;20(12):3554-61. doi: 10.1021/bi00515a039.
Ribosomal subunits were isolated from eggs or embryos of Urechis caupo, and the ribonucleic acid (RNA) was characterized by electrophoresis under denaturing conditions. The small ribosomal subunit contains a single 17S RNA sequence with a molecular weight of 6.20 X 10(5). The large ribosomal subunit contains four polynucleotide sequences. The 5S RNA has a molecular weight of 4.09 X 10(4). The 26S RNA complex isolated under nondenaturing conditions dissociates in the presence of formamide to yield a 5.8S RNA, molecular weight 5.46 X 10(4), and two approximately 17S and 17.5S RNA sequences with molecular weights of 6.04 X 10(5) and 6.61 X 10(5). The 17S and 17.5S RNAs of the large ribosomal subunits are formed in vivo from a 26S RNA precursor after assembly of the large ribosomal subunit. Large ribosomal subunits are transferred from the nucleus to the cytoplasm with the 26S RNA precursor intact. The hidden break to form the 17S and 17.5S RNAs is introduced in the cytoplasm. No intact 26S RNA could be detected in polysomes; this indicates that the conversion of the 26S RNA to the 17S and 17.5S RNAs may be required to produce large ribosomal subunits capable of participating in protein synthesis.
从星虫的卵或胚胎中分离出核糖体亚基，并在变性条件下通过电泳对核糖核酸（RNA）进行表征。小核糖体亚基包含一个分子量为6.20×10⁵的单一17S RNA序列。大核糖体亚基包含四个多核苷酸序列。5S RNA的分子量为4.09×10⁴。在非变性条件下分离的26S RNA复合物在甲酰胺存在下解离，产生分子量为5.46×10⁴的5.8S RNA，以及两个分子量分别为6.04×10⁵和6.61×10⁵的约17S和17.5S RNA序列。大核糖体亚基的17S和17.5S RNA在大核糖体亚基组装后由26S RNA前体在体内形成。大核糖体亚基完整地带着26S RNA前体从细胞核转移到细胞质中。形成17S和17.5S RNA的隐蔽断裂在细胞质中引入。在多核糖体中未检测到完整的26S RNA；这表明将26S RNA转化为17S和17.5S RNA可能是产生能够参与蛋白质合成的大核糖体亚基所必需的。
