Department of Chemistry and Biotechnology, Graduate School of Engineering, University of Tokyo, Tokyo, Japan.
Nat Chem Biol. 2010 Apr;6(4):277-82. doi: 10.1038/nchembio.323. Epub 2010 Feb 7.
A modified base at the first (wobble) position of some tRNA anticodons is critical for deciphering the genetic code. In eukaryotes and eubacteria, AUA codons are decoded by tRNAsIle with modified bases pseudouridine (and/or inosine) and lysidine, respectively. The mechanism by which archaeal species translate AUA codons is unclear. We describe a polyamine-conjugated modified base, 2-agmatinylcytidine (agm(2)C or agmatidine), at the wobble position of archaeal tRNA(Ile) that decodes AUA codons specifically. We demonstrate that archaeal cells use agmatine to synthesize agm(2)C of tRNA(Ile). We also identified a new enzyme, tRNA(Ile)-agm(2)C synthetase (TiaS), that catalyzes agm(2)C formation in the presence of agmatine and ATP. Although agm(2)C is chemically similar to lysidine, TiaS constitutes a distinct class of enzyme from tRNA(Ile)-lysidine synthetase (TilS), suggesting that the decoding systems evolved convergently across domains.
一些 tRNA 反密码子的第一（摆动）位置的修饰碱基对于破译遗传密码至关重要。在真核生物和原核生物中，AUA 密码子分别由携带修饰碱基假尿嘧啶（和/或肌苷）和赖氨酸的 tRNAIle 解码。古菌翻译 AUA 密码子的机制尚不清楚。我们描述了一种多胺缀合的修饰碱基，即位于古菌 tRNA（Ile）摆动位置的 2-胍基胞苷（agm(2)C 或胍丁啶），它特异性地解码 AUA 密码子。我们证明古菌细胞利用精胺合成 tRNA（Ile）的 agm(2)C。我们还鉴定了一种新的酶，tRNA（Ile）-agm(2)C 合成酶（TiaS），它在精胺和 ATP 的存在下催化 agm(2)C 的形成。尽管 agm(2)C 在化学上与赖氨酸相似，但 TiaS 与 tRNA（Ile）-赖氨酸合成酶（TilS）属于不同类别的酶，这表明解码系统在不同的域中是趋同进化的。
