X-ray crystallography of maturation and aminoacylation of transfer RNA

我们解决了参与tRNA成熟和转录后修饰的几种酶及其与tRNA的络合物的晶体结构。在处理步骤中，3‘-延长的拖尾序列被RNase PH修剪，如果RNase PH修剪掉tRNA结合氨基酸的CCA末端的一部分，则CCA添加酶(模板无关RNA聚合酶)修复CCA序列。Aquifex aeolicus RNase PH在2.3Å分辨率下的晶体结构)揭示了两个酶家族如何在没有任何核酸模板的情况下聚合定义的CCA三核苷酸。在转录后修饰过程中，在与tRNA形成的复合体中，考古核糖核糖核酸鸟嘌呤转移糖基酶的晶体结构(3.3Å分辨率)揭示了该酶是如何通过将规范的tRNA L形状变形为1形状来识别和修饰深埋的核苷酸的。TRNA(Gm18)甲基转移酶的1.85Å分辨晶体结构表明，催化折叠中的深结结构不仅构建了活性中心和辅因子结合部位，而且通过分子二聚促进了依赖于RNA的甲基化机制。对于氨基酰-tRNA合成酶，我们通过结晶学分析阐明了人色氨酰-tRNA合成酶细胞因子活性的结构基础，这是在酶的长期进化过程中获得的。

We solved crystal structures of several enzymes involved in tRNA maturation and post-transcriptional modification and their complex with tRNA. In the processing step, 3'-extended trailer sequence is trimmed by RNase PH, and, if RNase PH trims off a part of the amino-acid-attaching CCA terminus of tRNA, then CCA-adding enzyme (template-independent RNA polymerase) repairs the CCA sequence. Crystal structure of Aquifex aeolicus RNase PH at 2.3 Å resolution) reveals how two enzyme families have evolved to polymerize defined CCA trinucleotides without aid of any nucleic-acid template. In the post-transcriptional modification process, crystal structure (3.3 Å resolution) of archaeosine tRNA guanine transglycosylase in a complex with tRNA uncovered how the enzyme recognizes and modifies a deeply-buried nucleotide by deformation of canonical tRNA L-shape to 1 -shape. The 1.85 Å-resolution crystal structure of tRNA(gm18)methyltransferase revealed that the deep knot structure found in the catalytic fold not only constructs active-site and cofactor-binding site but also facilitates RNA-dependent methylation mechanism via molecular dimerization. For aminoacyl-tRNA synthetase, we elucidated the structural basis for the cytokine activity of human tryptophanyl-tRNA synthetase by crystallographic analysis, which has been gained in the long evolution of the enzyme.