10月28日，The  Journal  of  Biological  Chemistry在線發(fā)表了中科院上海生科院生化與細(xì)胞所王恩多研究組最新研究結(jié)果：亮氨酰-tRNA合成酶的CP2結(jié)構(gòu)域?qū)γ傅陌被岬幕罨娃D(zhuǎn)移后的編校非常重要,。

亮氨酰-tRNA合成酶(LeuRS)催化合成Leu-tRNALeu,，Leu-tRNALeu為蛋白質(zhì)的生物合成的原料。第一步反應(yīng)為氨基酸活化反應(yīng),；第二步反應(yīng)將活化的氨基酸轉(zhuǎn)移到tRNA的3'末端,，稱(chēng)為tRNA氨基酰化反應(yīng)。LeuRS必須精確地識(shí)別亮氨酸,，但細(xì)胞中普遍存在20種形成蛋白質(zhì)的氨基酸、大量的非蛋白質(zhì)氨基酸和氨基酸類(lèi)似物,，LeuRS進(jìn)化出編校功能(editing)水解被誤活化或誤氨基?；姆菍?duì)應(yīng)氨基酸(例如異亮氨酸)。

王恩多研究組的博士研究生周小龍等用來(lái)自真細(xì)菌(E.  coli),、古細(xì)菌(P.  horikoshii)以及單細(xì)胞低等真核生物賈第蟲(chóng)(G.  lamblia)的LeuRS作為研究對(duì)象,，證明了三界LeuRS中的一個(gè)構(gòu)象保守、但一級(jí)結(jié)構(gòu)和插入位置不同的一段稱(chēng)為CP2結(jié)構(gòu)域(Connective  Peptide  2  domain)插入肽段對(duì)于LeuRS的氨基酸活化和編校功能至關(guān)重要,，同時(shí)與酶和tRNALeu結(jié)合的親和力有關(guān),。研究人員進(jìn)一步通過(guò)丙氨酸酸掃描(Ala  scanning)和點(diǎn)突變的方法找到了CP2結(jié)構(gòu)域內(nèi)對(duì)以上功能起關(guān)鍵作用的氨基酸殘基，并闡明了它們發(fā)揮作用的機(jī)理,。通過(guò)嵌合酶研究,，他們還發(fā)現(xiàn)：來(lái)自古細(xì)菌P.  horikoshii的LeuRS的CP2結(jié)構(gòu)域可部分代替GlLeuRS的CP2結(jié)構(gòu)域的功能，但是來(lái)自真細(xì)菌的EcLeuRS的CP2結(jié)構(gòu)域卻不能代替,，揭示了CP2結(jié)構(gòu)域在LeuRS上的插入位點(diǎn)對(duì)于其發(fā)揮生物學(xué)功能是非常重要的,。（生物谷Bioon.com）

生物谷推薦原始出處：

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.