Institut für Biochemie, Bayerische Julius-Maximilians-Universität, Röntgenring 11, D-8700 Würzburg, FRG.
EMBO J. 1984 May;3(5):1091-6. doi: 10.1002/j.1460-2075.1984.tb01934.x.
Translation of tobacco mosaic virus (TMV) RNA in tobacco protoplasts yields the 17.5-K coat protein, a 126-K protein and a 183-K protein which is generated by an efficient readthrough over the UAG termination codon at the end of the 126-K cistron. In wheat germ extracts, however, only the 5'-proximal 126-K cistron is translated whereas the 183-K readthrough protein is not synthesized. Purification and sequence analysis of the endogenous tyrosine tRNAs revealed that the uninfected tobacco plant contains two tRNAs, both with GPsiA anticodons which stimulate the UAG readthrough in vitro and presumably in vivo. In contrast, 85% of the tRNA from wheat germ contains a QPsiA anticodon and 15% has a GPsiA anticodon. Otherwise the sequences of tRNAs from wheat germ and tobacco are identical. UAG readthrough and hence synthesis of the 183-K protein is only stimulated by tRNA(GPsiA) and not at all by tRNA(QPsiA). The tRNAs from wheat leaves were also sequenced. This revealed that adult wheat contains tRNA(GPsiA) only. This is very much in contrast to the situation in animals, where Q-containing tRNAs are characteristic for adult tissues whereas Q deficiency is typical for the neoplastic and embryonic state.
在烟草原生质体中转译烟草花叶病毒（TMV）RNA 可产生 17.5-K 外壳蛋白、126-K 蛋白和 183-K 蛋白，这是通过在 126-K 顺反子末端的 UAG 终止密码子上进行有效的通读而产生的。然而，在小麦胚提取物中，只有 5'-近端的 126-K 顺反子被转译，而 183-K 通读蛋白则未被合成。内源性酪氨酸 tRNA 的纯化和序列分析表明，未感染的烟草植物含有两种 tRNA，都具有刺激 UAG 通读的 GPsiA 反密码子，推测在体内也是如此。相比之下，85%的来自小麦胚的 tRNA 含有 QPsiA 反密码子，而 15%的含有 GPsiA 反密码子。否则，小麦和烟草的 tRNA 序列完全相同。只有 tRNA(GPsiA)可刺激 UAG 通读并合成 183-K 蛋白，而 tRNA(QPsiA)则完全不能。小麦叶片的 tRNA 也被测序。这表明成年小麦只含有 tRNA(GPsiA)。这与动物中的情况形成鲜明对比，在动物中，含有 Q 的 tRNA 是成年组织的特征，而 Q 缺乏是肿瘤和胚胎状态的典型特征。
