Nilsson Michaela, Rydén-Aulin Monica
Department of Microbiology, Stockholm University, S-106 91, Stockholm, Sweden.
Biochim Biophys Acta. 2003 May 13;1627(1):1-6. doi: 10.1016/s0167-4781(03)00050-2.
Readthrough of the nonsense codons UAG, UAA, and UGA is seen in Escherichia coli strains lacking tRNA suppressors. Earlier results indicate that UGA is miscoded by tRNA(Trp). It has also been shown that tRNA(Tyr) and tRNA(Gln) are involved in UAG and UAA decoding in several eukaryotic viruses as well as in yeast. Here we have investigated which amino acid(s) is inserted in response to the nonsense codons UAG and UAA in E. coli. To do this, the stop codon in question was introduced into the staphylococcal protein A gene. Protein A binds to IgG, which facilitates purification of the readthrough product. We have shown that the stop codons UAG and UAA direct insertion of glutamine, indicating that tRNA(Gln) can read the two codons. We have also confirmed that tryptophan is inserted in response to UGA, suggesting that it is read by tRNA(Trp).
在缺乏tRNA抑制子的大肠杆菌菌株中可观察到对无义密码子UAG、UAA和UGA的通读现象。早期结果表明UGA可被tRNA(Trp)误编码。研究还表明，tRNA(Tyr)和tRNA(Gln)在几种真核病毒以及酵母中参与UAG和UAA的解码。在此，我们研究了在大肠杆菌中，针对无义密码子UAG和UAA会插入哪种氨基酸。为此，将相关的终止密码子引入葡萄球菌蛋白A基因中。蛋白A与IgG结合，这便于对通读产物进行纯化。我们已表明，终止密码子UAG和UAA指导谷氨酰胺的插入，这表明tRNA(Gln)能够识别这两个密码子。我们还证实，色氨酸会响应UGA而插入，这表明它是由tRNA(Trp)识别的。
