10月28日，The Journal of Biological Chemistry在线发表了中科院上海生科院生化与细胞所王恩多研究组最新研究结果：亮氨酰-tRNA合成酶的CP2结构域对酶的氨基酸的活化和转移后的编校非常重要。
亮氨酰-tRNA合成酶(LeuRS)催化合成Leu-tRNALeu，Leu-tRNALeu为蛋白质的生物合成的原料。第一步反应为氨基酸活化反应；第二步反应将活化的氨基酸转移到tRNA的3'末端，称为tRNA氨基酰化反应。LeuRS必须精确地识别亮氨酸，但细胞中普遍存在20种形成蛋白质的氨基酸、大量的非蛋白质氨基酸和氨基酸类似物，LeuRS进化出编校功能(editing)水解被误活化或误氨基酰化的非对应氨基酸(例如异亮氨酸)。
王恩多研究组的博士研究生周小龙等用来自真细菌(E. coli)、古细菌(P. horikoshii)以及单细胞低等真核生物贾第虫(G. lamblia)的LeuRS作为研究对象，证明了三界LeuRS中的一个构象保守、但一级结构和插入位置不同的一段称为CP2结构域(Connective Peptide 2 domain)插入肽段对于LeuRS的氨基酸活化和编校功能至关重要，同时与酶和tRNALeu结合的亲和力有关。研究人员进一步通过丙氨酸酸扫描(Ala scanning)和点突变的方法找到了CP2结构域内对以上功能起关键作用的氨基酸残基，并阐明了它们发挥作用的机理。通过嵌合酶研究，他们还发现：来自古细菌P. horikoshii的LeuRS的CP2结构域可部分代替GlLeuRS的CP2结构域的功能，但是来自真细菌的EcLeuRS的CP2结构域却不能代替，揭示了CP2结构域在LeuRS上的插入位点对于其发挥生物学功能是非常重要的。（生物谷Bioon.com）
生物谷推荐原始出处：
J. Biol. Chem, 10.1074/jbc.M806745200
The CP2 domain of leucyl-tRNA synthetase is crucial for amino acid activation and post-transfer editing
Xiao-Long Zhou, Bin Zhu, and En-Duo Wang
Key Laboratory of Molecular Biology, Inst of Biochem and Cell Biol, Shanghai Insts for Biolog Sci,The Chinese Academy of Sciences, Shanghai 200031
Leucyl-tRNA synthetase (LeuRS) has an insertion domain, called connective peptide 2 (CP2), either directly preceding or following the editing domain (CP1 domain), depending on the species. The global structures of the CP2 domains from all LeuRSs are similar. Although the CP1 domain has been extensively explored to be responsible for hydrolysis of mischarged tRNALeu, the role of the CP2 domain remains undefined. In the present work, deletion of the CP2 domain of Giardia lamblia LeuRS (GlLeuRS) showed that the CP2 domain is indispensable for amino acid activation, post-transfer editing; and contributes to LeuRS-tRNALeu binding affinity. In addition, its functions are conserved in both eukaryotic/archaeal and prokaryotic LeuRSs from G. lamblia, Pyrococcus horikoshii (PhLeuRS), and Escherichia coli (EcLeuRS). Alanine scanning and site-directed mutagenesis assays of the CP2 domain identified several residues which are crucial for its functions. Data from the chimeric mutants, which replaced the CP2 domain of GlLeuRS with either PhLeuRS or EcLeuRS, showed that the CP2 domain of PhLeuRS but not that of EcLeuRS can partially restore amino acid activation and post-transfer editing functions; suggesting that the functions of the CP2 domain are dependent on its location in the primary sequence of LeuRS.
