Jacobson L A, Baldassare J C
J Bacteriol. 1976 Jul;127(1):637-43. doi: 10.1128/jb.127.1.637-643.1976.
The complexed 70S ribosomes (monosomes) that accumulate in Escherichia coli after an energy source shift-down were examined in an electron microscope. In all cases, the ribosomes lie at or near one end of a ribonucleic acid (RNA) strand. This messenger RNA (mRNA) has a mean length of 168 nm and a length-average length of 200 nm, sufficient to code for polypeptides of a weight-average molecular weight of 20,000. The length distribution indicates that these strands are a reasonable representation of the population of monocistronic mRNA's of E. coli. The mRNA strands disappear entirely upon digestion with pancreatic ribonuclease, phosphodiesterase I, or polynucleotide phosphorylase. The susceptibility to digestion by 3'-exonucleases indicate that the ribosomes lie at the 5' end of the mRNA strands. These results are consistent with the hypothesis that down-shifted cells have a translational defect at a point subsequent to the binding of ribosomes to mRNA but prior to the formation of the first peptide bond, such that ribosomes remain bound at or near their points of initial attachment to mRNA.
对能量源下调后在大肠杆菌中积累的复合70S核糖体（单核糖体）进行了电子显微镜检查。在所有情况下，核糖体位于核糖核酸（RNA）链的一端或其附近。这种信使RNA（mRNA）的平均长度为168纳米，长度平均为200纳米，足以编码重均分子量为20,000的多肽。长度分布表明这些链是大肠杆菌单顺反子mRNA群体的合理代表。用胰核糖核酸酶、磷酸二酯酶I或多核苷酸磷酸化酶消化后，mRNA链完全消失。对3' - 外切核酸酶消化的敏感性表明核糖体位于mRNA链的5'端。这些结果与以下假设一致：能量下调的细胞在核糖体与mRNA结合之后但在第一个肽键形成之前的某个点存在翻译缺陷，使得核糖体保持结合在其初始附着到mRNA的点或其附近。
