大肠杆菌色氨酸tRNA的身份决定因素。
Identity determinants of E. coli tryptophan tRNA.
作者信息
Himeno H, Hasegawa T, Asahara H, Tamura K, Shimizu M
机构信息
Institute of Space and Astronautical Science, Kanagawa, Japan.
出版信息
Nucleic Acids Res. 1991 Dec 11;19(23):6379-82. doi: 10.1093/nar/19.23.6379.
The first base pair of the acceptor stem A1-U72 and the discriminator base G73, as well as the anticodon nucleotides, characterize the tryptophan tRNA in E. coli. To determine the contribution of these nucleotides to the tryptophan acceptor activity, various transcripts of E. coli tryptophan tRNA mutants were constructed. Substitutions of the discriminator base G73, which is conserved within prokaryotic tryptophan tRNAs, impaired aminoacylation with tryptophan. Substitutions of other purine-pyrimidine pairs for A1-U72 revealed that only U72 weakly contributed to recognition by tryptophanyl-tRNA synthetase. The E. coli aspartic acid tRNA transcript introducing the tryptophan anticodon CCA showed almost the same tryptophan charging activity as the tryptophan tRNA transcript possessing a G1-C72 base pair. Only a low activity was detected in the mutant tryptophan tRNA transcript possessing a set of G1-C72 and A73, which is observed in eukaryotic tryptophan tRNAs. These results indicate that the anticodon and G73 are major identity determinants of tryptophan tRNA in E. coli, whereas the A1-U72 base pair is only a weak recognition element.
受体茎的第一个碱基对A1-U72和判别碱基G73，以及反密码子核苷酸，是大肠杆菌中色氨酸tRNA的特征。为了确定这些核苷酸对色氨酸受体活性的贡献，构建了大肠杆菌色氨酸tRNA突变体的各种转录本。判别碱基G73在原核生物色氨酸tRNA中是保守的，其替换会损害色氨酸的氨酰化作用。用其他嘌呤-嘧啶对替换A1-U72发现，只有U72对色氨酰-tRNA合成酶的识别作用较弱。引入色氨酸反密码子CCA的大肠杆菌天冬氨酸tRNA转录本显示出与具有G1-C72碱基对的色氨酸tRNA转录本几乎相同的色氨酸负载活性。在具有G1-C72和A73的突变色氨酸tRNA转录本中仅检测到低活性，这种组合在真核生物色氨酸tRNA中可见。这些结果表明，反密码子和G73是大肠杆菌中色氨酸tRNA的主要识别决定因素，而A1-U72碱基对只是一个较弱的识别元件。
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