亮氨酰-tRNA合成酶在体内负责催化亮氨酸和对应tRNA之间的酯化反应，生成亮氨酰-tRNA为蛋白质生物合成提供原料。根据特定插入序列在结构中的空间位置以及有无特征的延伸结构域，亮氨酰-tRNA合成酶被划分为细菌类、古菌类和真核类。与原核来源的亮氨酰-tRNA合成酶相比，真核以及古菌类亮氨酰-tRNA合成酶在进化的过程中获得了许多独特的功能未知的结构元件，亮氨酸专一结构域1( leucine-specific-domain 1,LSD-1）就是其中之一。
中科院上海生命科学研究院生物化学与细胞生物学研究所王恩多研究组近日在Biochemical Journal上发表了该小组最新研究论文：原核与真核生物亮氨酰-tRNA合成酶的亮氨酸专一结构域1的功能鉴定。
王恩多实验室的周小龙博士研究了古菌和真核来源的亮氨酰-tRNA合成酶的LSD-1元件，结果发现，在古菌和真核亮氨酰-tRNA合成酶共有的LSD-1区域引入突变时会显著降低酶的氨基酸活化活力，而几乎不影响tRNA氨基酰化的活力。但将真核亮氨酰-tRNA合成酶的LSD-1特有的延长部分突变后会严重影响其tRNA氨基酰化活力。
该研究揭示了LSD-1结构域在亮氨酰-tRNA合成酶催化过程的作用：不参与转移后编校反应，维持了tRNA氨基酰化所需要的构象。
该研究工作得到中国科学院、科技部重大科学研究计划、国家自然科学基金委以及上海市科委的资助。（生物谷Bioon.com）
生物谷推荐原文出处：
Biochem.J. doi:10.1042/BJ20100474
Post-transfer editing by a eukaryotic leucyl-tRNA synthetase resistant to the broad-spectrum drug AN2690
Xiao-Long Zhou, Min Tan, Meng Wang, Xin Chen and En-Duo Wang1
State Key Laboratory of Molecular Biology and Graduate School of the Chinese Academy of Sciences, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, The Chinese Academy of Sciences, 320 Yue Yang Road, Shanghai 200031, People's Republic of China
Some aaRSs (aminoacyl-tRNA synthetases) develop editing mechanisms to correct mis-charged tRNA. The CP1 (connective peptide 1) domain of LeuRS (leucyl-tRNA synthetase) contains the editing active site, which is the proven target for the broad-spectrum drug AN2690 (5-fluoro-1,3-dihydro-1-hydroxy-2,1-benzoxaborole). The ESI (eukarya-specific insertion 1) in the CP1 domain of GlLeuRS (Giardia lamblia LeuRS) has been identified. Similar substitution with the ESI from HsLeuRS (Homo sapiens LeuRS) impeded the leucine activation, aminoacylation and post-transfer editing of the enzyme, but had no effect on the editing specificity toward non-specific amino acids. Thr341 in GlLeuRS served as a specificity discriminator, as found in other LeuRS systems, although its substitution with an alanine residue did not destroy Leu-tRNALeu synthesis in vitro and in vivo. The Arg338 was crucial for tRNALeu charging and the Asp440 was crucial for leucine activation and aminoacylation. The post-transfer editing required the CTD (C-terminal domain), Arg338 and Asp440 of GlLeuRS. Interestingly, GlLeuRS was completely resistant to the AN2690, which is an inhibitor of various LeuRSs. The universally conserved aspartate residue in the LeuRS CP1 domains was responsible for the resistance of GlLeuRS and another recently reported AN2690-resistant AaLeuRS (Aquifex aeolicus LeuRS). Our results indicate the functional divergence of some absolutely conserved sites, improve the understanding of the editing function of eukaryotic/archaeal LeuRSs and shed light on the development of a GlLeuRS-specific inhibitor for the treatment of giardiasis.
