Department of Chemistry and Biotechnology, Graduate School of Engineering, University of Tokyo, Tokyo, Japan.
Nat Struct Mol Biol. 2011 Oct 16;18(11):1268-74. doi: 10.1038/nsmb.2121.
The archaeal AUA-codon specific tRNA(Ile) contains 2-agmatinylcytidine (agm(2)C or agmatidine) at the anticodon wobble position (position 34). The formation of this essential modification is catalyzed by tRNA(Ile)-agm(2)C synthetase (TiaS) using agmatine and ATP as substrates. TiaS has a previously unknown catalytic domain, which we have named the Thr18-Cyt34 kinase domain (TCKD). Biochemical analyses of Archaeoglobus fulgidus TiaS and its mutants revealed that the TCKD first hydrolyzes ATP into AMP and pyrophosphate, then phosphorylates the C2 position of C34 with the γ-phosphate. Next, the amino group of agmatine attacks this position to release the phosphate and form agm(2)C. Notably, the TCKD also autophosphorylates the Thr18 of TiaS, which may be involved in agm(2)C formation. Thus, the unique kinase domain of TiaS catalyzes dual phosphorylation of protein and RNA substrates.
古菌的 AUA-codon 特异性 tRNA(Ile)在反密码子摆动位置（第 34 位）含有 2-胍基胞苷 (agm(2)C 或胍基丁啶)。这种必需修饰的形成由 tRNA(Ile)-agm(2)C 合成酶 (TiaS) 催化，使用胍基丁氨酸和 ATP 作为底物。TiaS 具有一个以前未知的催化结构域，我们将其命名为 Thr18-Cyt34 激酶结构域 (TCKD)。对古生菌 A.fulgidus TiaS 及其突变体的生化分析表明，TCKD 首先将 ATP 水解为 AMP 和焦磷酸，然后用 γ-磷酸将 C34 的 C2 位置磷酸化。接下来，胍基丁氨酸的氨基攻击该位置，释放磷酸并形成 agm(2)C。值得注意的是，TCKD 还使 TiaS 的 Thr18 自身磷酸化，这可能参与了 agm(2)C 的形成。因此，TiaS 的独特激酶结构域催化蛋白质和 RNA 底物的双重磷酸化。
