Dean J R, Sykes J
Biochem J. 1974 Jun;140(3):443-50. doi: 10.1042/bj1400443.
The suggested involvement of ribonuclease II in the maturation of rRNA has been examined directly by determining the activity of the enzyme and the amount of p16S rRNA in cell-free extracts from Escherichia coli A19 and its temperature-sensitive derivative N464 grown under experimental conditions designed to vary the amounts of enzyme and precursor independently. In strain A19 the enzyme showed maximum activity in circumstances where the amount of p16S rRNA was normal (e.g. exponential-phase cells) or raised eight times (e.g. during inhibition of growth by methionine starvation of the relaxed auxotroph or by chloramphenicol or puromycin treatment). In strain N464 at the non-permissive temperature the ribonuclease II activity may be decreased by 50% without effect upon the amount of p16S rRNA, whereas in methionine starvation of this strain the enzyme activity is at a maximum and the p16S rRNA is eight times that in exponential-phase cells. These observations are discussed in relation to the previously implied role of ribonuclease II in the maturation of rRNA within ribosome precursors.
通过测定核糖核酸酶II的活性以及来自大肠杆菌A19及其温度敏感衍生物N464的无细胞提取物中p16S rRNA的量，直接检验了核糖核酸酶II参与rRNA成熟过程的假设。这两种菌株在旨在独立改变酶和前体数量的实验条件下培养。在菌株A19中，当p16S rRNA的量正常时（如指数生长期细胞）或增加八倍时（如在松弛营养缺陷型经甲硫氨酸饥饿抑制生长期间，或经氯霉素或嘌呤霉素处理时），该酶表现出最大活性。在菌株N464中，在非允许温度下，核糖核酸酶II的活性可能降低50%，而p16S rRNA的量不受影响；然而，在该菌株的甲硫氨酸饥饿状态下，酶活性最高，且p16S rRNA是指数生长期细胞中的八倍。结合核糖核酸酶II在核糖体前体中rRNA成熟过程中先前暗示的作用，对这些观察结果进行了讨论。
