Hill C W, Combriato G, Dolph W
J Bacteriol. 1974 Feb;117(2):351-9. doi: 10.1128/jb.117.2.351-359.1974.
The Escherichia coli suppressor mutation, supT, has been shown to cause a C --> U substitution in the middle position of the tRNA(GGG) (Gly) anticodon. This is the same tRNA species that is altered by the glyUsu(AGA) mutation studied previously. This finding indicates that the supT mutant tRNA reads the glutamic acid codon, GAG. The supT suppressor has also been converted to a new suppressor, called glyUsu(GAA), which will suppress the GAA mutation, trpA46. The in vivo suppression efficiencies of each of these three missense suppressors has been measured and are as follows: glyUsu(AGA), 3.6%; supT, 1.6%; and glyUsu(GAA), 0.4%. Mistranslation by these mutant glycine tRNA species has no adverse affects on cell growth since cultures possessing the suppressors grow as fast as cells without. The supT tRNA species can be observed as a peak in the profile of glycyl-tRNA fractionated on a RPC-5 chromatographic column, indicating that the mutant tRNA can be aminoacylated with reasonable efficiency. This finding contrasts with previous findings concerning the glyUsu(AGA) mutant tRNA which is not significantly aminoacylated under the same conditions.
大肠杆菌抑制突变体supT已被证明会导致tRNA(GGG)(甘氨酸)反密码子中间位置发生C→U替换。这与之前研究的glyUsu(AGA)突变所改变的是同一种tRNA。这一发现表明，supT突变型tRNA识别谷氨酸密码子GAG。supT抑制子也已被转化为一种新的抑制子，称为glyUsu(GAA)，它将抑制GAA突变trpA46。已测定这三种错义抑制子各自在体内的抑制效率，结果如下：glyUsu(AGA)为3.6%；supT为1.6%；glyUsu(GAA)为0.4%。这些突变型甘氨酸tRNA造成的错义翻译对细胞生长没有不利影响，因为含有这些抑制子的培养物与不含抑制子的细胞生长速度一样快。在RPC - 5色谱柱上分级分离的甘氨酰 - tRNA图谱中，可以观察到supT tRNA呈现为一个峰，这表明突变型tRNA能够以合理的效率进行氨酰化。这一发现与之前关于glyUsu(AGA)突变型tRNA的研究结果形成对比，在相同条件下，glyUsu(AGA)突变型tRNA的氨酰化程度不显著。
