Tai P C, Wallace B J, Davis B D
Proc Natl Acad Sci U S A. 1978 Jan;75(1):275-9. doi: 10.1073/pnas.75.1.275.
The induction of misreading by streptomycin in vitro, previously observed with synthetic messengers, is now demonstrated with natural (endogenous or viral) messenger by the use of extracts of temperature sensitive mutants lacking Glu--tRNA or Val--tRNA synthetase. With chain-elongating but noninitiating ribosomes (i.e., purified polysomes) deprived of an aminoacyl--tRNA, streptomycin and other aminoglycosides, over a wide range of concentrations, stimulate incorporation. With ribosomes initiating in the presence of streptomycin stimulation is also observed but it is restricted, just like phenotypic suppression in cells, to very low streptomycin concentrattions which evidently allow some ribosomes to initiate and later encounter them in the course of chain elongation. The stimulation is accompanied by an increase in the size of the products; hence, it is evidently due to substitution of an incorrect aminoacyl--tRNA for a missing one. The test introduced here also has revealed a misreading effect of streptomycin on resistant ribosomes. In addition, significant intrinsic misreading was observed without streptomycin, indicating that under optimal conditions for in vitro protein synthesis an empty codon is frequently read by an incorrect aminoacyl--tRNA.
链霉素在体外诱导错读，此前在合成信使中观察到这种现象，现在通过使用缺乏谷氨酰胺 - tRNA或缬氨酸 - tRNA合成酶的温度敏感突变体提取物，在天然（内源性或病毒）信使中得到了证实。对于缺乏氨酰 - tRNA的链延伸但不起始的核糖体（即纯化的多核糖体），链霉素和其他氨基糖苷类药物在很宽的浓度范围内都会刺激掺入。对于在链霉素存在下起始的核糖体，也观察到了刺激作用，但这种刺激作用受到限制，就像细胞中的表型抑制一样，仅限于非常低的链霉素浓度，显然这使得一些核糖体能够起始，随后在链延伸过程中遇到链霉素。这种刺激伴随着产物大小的增加；因此，这显然是由于用不正确的氨酰 - tRNA替代了缺失的氨酰 - tRNA。这里介绍的试验还揭示了链霉素对抗性核糖体的错读效应。此外，在没有链霉素的情况下观察到了显著的内在错读，这表明在体外蛋白质合成的最佳条件下，空密码子经常被不正确的氨酰 - tRNA读取。
