Structural basis for RNA function in ribonucleoprotein complex

蛋白质与rna结合并协同形成核糖核蛋白，在高度特异性的遗传信息传递过程中起作用。在本研究中，我们首先关注tRNA加工和翻译后修饰。我们在每个反应步骤中解析了cca加酶与tRNA引物络合的晶体结构（Nature, 2006）， MnmA硫脲合成酶与tRNA络合的三个反应步骤（Nature, 2006）， TilS赖苷合成酶与tRNA^<Ile2> (Nature, 2009)，并在原子分辨率上揭示了它们的动态RNA识别和催化机制。其次，在真核生物和古细菌中，tRNA修饰和激活酶与其同源tRNA形成通道核糖核蛋白复合物，完成复杂的顺序化学反应。我们解决了trna依赖性氨基转移酶GatDE与tRNAGIn复合物的晶体结构，以显示该复合物如何催化三个连续反应（Science, 2006）。我们进一步解决了真核和古细菌tRNA^<Phe> (j.l l. biol) 37位yW超修饰合成过程中5个酶中的3个酶的晶体结构。， 2008；核酸研究，2009；Proc.Natl.Acad.Sci。美国,2009年)。这些研究揭示了每种酶如何以不同的方式利用s -腺苷-蛋氨酸辅因子来实现顺序修饰反应。最后，我们解决了Sec易位机制的晶体结构和生化分析，该机制在细胞质中跨膜易位中起作用（Nature, 2009）。因此，我们发现SecYE通道和SecA分子马达的构象相互转换，从封闭形态变为开放形态，并相互激活以实现蛋白质易位。

Proteins associate and collaborate with RNAs to form ribonucleoproteins, which act in highly specific genetic information transfer process. In this study, we first focused on tRNA processing and post-translational modification. We solved the crystal structures of CCA-adding enzymes complexed with tRNA primer at each reaction step (Nature, 2006), MnmA thiouridine synthetase complexed with tRNA in three reaction steps (Nature, 2006), and TilS lysidine synthetase complexed with tRNA^<Ile2> (Nature, 2009) and revealed their dynamic RNA recognition and catalytic mechanism at an atomic resolution. Second, in eukarya and archaea, tRNA modifying and activating enzymes form channeling ribonucleoprotein complex with their cognate tRNA to fulfil the complex sequential chemical reactions. We solved the crystal structure of tRNA-dependent amidotransferase GatDE in a complex with tRNAGIn to show how the complex catalyzes three sequential reactions (Science, 2006). We further solved the crystal strictures of 3 out of 5 enzymes involved in synthesis of yW hypermodification in position 37 of eukaryotic and archaeal tRNA^<Phe> (J.Mol.Biol., 2008 ; Nucleic Acids Res., 2009 ; Proc.Natl.Acad.Sci.USA, 2009). These studies revealed how each enzyme utilizes S-adenosyl-methionine cofactor in different way to achieve the sequential modification reaction. Finally, we solved the crystal structure as well as biochemical analysis of Sec translocon machinery, acting in translocation of thus synthesized protein in cytoplasm across the membrane (Nature, 2009). We thus showed that SecYE channel and SecA molecular motor mutually transit their conformation from closed to open form to activate each other to achieve the protein translocation.