Breitschopf K, Gross H J
Institut für Biochemie, Bayerische Julius-Maximilians-Universität, Würzburg, Germany.
EMBO J. 1994 Jul 1;13(13):3166-9. doi: 10.1002/j.1460-2075.1994.tb06615.x.
Transfer RNA (tRNA) identify is maintained by the highly specific interaction of a few defined nucleotides or groups of nucleotides, called identity elements, with the cognate aminoacyl-tRNA synthetase, and by nonproductive interactions with the other 19 aminoacyl-tRNA synthetases. Most tRNAs have a set of identity elements in at least two locations, commonly in the anticodon loop or in the acceptor stem, and at the discriminator base position 73. We have used T7 RNA polymerase transcribed tRNAs to demonstrate that the sole replacement of the discriminator base A73 of human tRNA(Leu) with the tRNA(Ser)-specific G generates a complete identity switch to serine acceptance. The reverse experiment, the exchange of G73 in human tRNA(Ser) for the tRNA(Leu-specific A, causes a total loss of serine specificity without creating any leucine acceptance. These results suggest that the discriminator base A73 of human tRNA(Leu) alone protects this tRNA against serylation by seryl-tRNA synthetase. This is the first report of a complete identity switch caused by an exchange of the discriminator base alone.
转运RNA（tRNA）的识别是通过少数特定的核苷酸或核苷酸基团（称为识别元件）与同源氨酰tRNA合成酶之间的高度特异性相互作用，以及与其他19种氨酰tRNA合成酶的非生产性相互作用来维持的。大多数tRNA在至少两个位置有一组识别元件，通常在反密码子环或接受茎中，以及在鉴别碱基位置73处。我们使用T7 RNA聚合酶转录的tRNA来证明，将人tRNA（Leu）的鉴别碱基A73单独替换为tRNA（Ser）特异性的G会导致完全转变为接受丝氨酸。反向实验，将人tRNA（Ser）中的G73替换为人tRNA（Leu）特异性的A，会导致丝氨酸特异性完全丧失，且不会产生任何亮氨酸接受。这些结果表明，人tRNA（Leu）的鉴别碱基A73单独保护该tRNA不被丝氨酰tRNA合成酶丝氨酰化。这是关于仅通过鉴别碱基交换导致完全识别转变的首次报道。
