Yarus M, Cline S, Raftery L, Wier P, Bradley D
J Biol Chem. 1986 Aug 15;261(23):10496-505.
We have reciprocally transplanted the anticodon arm sequences of a set of amber suppressor tRNA genes, using recombinant DNA techniques. By this means, a very efficient suppressor may be converted to a poor one, and the poorest tRNA to the efficiency of the best one. In tRNA molecules of normal 2 degrees and 3 degrees structure, the suppressor efficiencies of different composite tRNAs having the same anticodon arm sequence are approximately the same. Large numbers of simultaneous changes throughout the rest of the molecule do not affect the efficiency. Selective nucleotide modification as a result of varied anticodon arm sequences cannot explain these efficiencies. Efficiencies are also unlikely to differ because of selective aminoacylation. Measurement of in vivo tRNA shows, however, that tRNA levels do vary if the anticodon arm sequence is changed. If tRNA levels are normalized, the anticodon arm effect on the translational efficiency remains. Therefore, different anticodon arms, all of normal secondary structure, are not equivalent in translation. The most efficient sequences in this series resemble those found in natural tRNAs associated with similar anticodons, as is proposed in the extended anticodon theory (Yarus, M. (1982) Science 218, 646-652). These molecules also provide some information on the specificity of nucleotide modification enzymes and on determinants of the steady-state tRNA level.
我们利用重组DNA技术对一组琥珀抑制tRNA基因的反密码子臂序列进行了相互移植。通过这种方式，一个非常高效的抑制子可能会转变为低效抑制子，而最差的tRNA则可能具有最佳tRNA的效率。在具有正常二级和三级结构的tRNA分子中，具有相同反密码子臂序列的不同复合tRNA的抑制效率大致相同。分子其余部分大量同时发生的变化不会影响效率。由于反密码子臂序列不同导致的选择性核苷酸修饰无法解释这些效率差异。效率也不太可能因选择性氨酰化而不同。然而，体内tRNA的测量结果表明，如果改变反密码子臂序列，tRNA水平确实会发生变化。如果将tRNA水平标准化，反密码子臂对翻译效率的影响仍然存在。因此，所有具有正常二级结构的不同反密码子臂在翻译中并不等效。该系列中最有效的序列类似于在与相似反密码子相关的天然tRNA中发现的序列，正如扩展反密码子理论（Yarus, M. (1982) Science 218, 646 - 652）中所提出的那样。这些分子还提供了一些关于核苷酸修饰酶特异性以及稳态tRNA水平决定因素的信息。
