近日,，英國《生物化學(xué)雜志》在線發(fā)表了生化與細(xì)胞所題為“Human cytoplasmic ProX edits mischarged tRNAPro with amino acid but not tRNA specificity”的最新研究成果，報道了人胞質(zhì)ProX編校誤氨基酰-tRNAPro的機理。
氨基酰-tRNA合成酶（aminoacyl-tRNA synthetase, aaRS）是一類古老的多結(jié)構(gòu)域蛋白質(zhì)家族,，催化tRNA的氨基?；磻?yīng),，生成氨基酰-tRNA (aminoacyl-tRNA)，為蛋白質(zhì)生物合成提供原料。根據(jù)aaRS一級序列中的特征結(jié)構(gòu)花式(motifs)以及催化功能域拓?fù)浣Y(jié)構(gòu),，20種aaRS被分為兩類,，I類酶和II類酶各10種,。研究人員發(fā)現(xiàn)，存在一類蛋白質(zhì)分子,，它們的一級序列中包含了aaRS的特征結(jié)構(gòu)花式,，或者在三級結(jié)構(gòu)上含有aaRS的某些特征結(jié)構(gòu)域。這類蛋白質(zhì)分子稱為類氨基酰-tRNA合成酶（類aaRS）,。與aaRS的經(jīng)典功能相比,，類aaRS的功能多樣，包括蛋白質(zhì)翻譯控制,、參與氨基酸合成和強化DNA合成等等,。
一般認(rèn)為，aaRS的祖先蛋白質(zhì)分子以核心酶（core enzyme）存在，行使基本的催化功能,。如今的aaRS是通過在該祖先核心酶在進(jìn)化中逐漸插入其它結(jié)構(gòu)域成為具有更多功能的酶而來,。目前自然界所有已知的aaRS中，多數(shù)都有一些附加結(jié)構(gòu)域,，與tRNA識別,、氨基酰化和編校相關(guān),。序列和結(jié)構(gòu)類似性分析表明,，類aaRS會在進(jìn)化過程的不同階段被aaRS的核心酶招募，成為當(dāng)今aaRS的新結(jié)構(gòu)域,。獨立存在的蛋白質(zhì)分子ProX,，廣泛存在于多種物種中，與來源于細(xì)菌的脯氨酰-tRNA合成酶（ProRS）的順式編校結(jié)構(gòu)域(INS)同源,。
王恩多研究組博士研究生阮亮亮,、副研究員周小龍等研究了人細(xì)胞質(zhì)ProX（HsProX）基因HsproX在人的9株不同的細(xì)胞系中的轉(zhuǎn)錄水平，首次通過HsProX的基因克隆和高表達(dá)得到了高純度的蛋白質(zhì),，研究了HsProX的編校功能,。研究結(jié)果表明HsProX可以專一水解誤氨基酰化的Ala-tRNAPro,；雖然tRNA的CCA76末端對HsProX的編?；盍χ陵P(guān)重要，但沒有tRNA的底物特異性,。另外,，鑒定了影響HsProX編校活力的關(guān)鍵氨基酸殘基,。
該工作得到了國家自然科學(xué)基金,、國家重大科學(xué)研究計劃、中國科學(xué)院上海生命科學(xué)研究院優(yōu)秀青年人才領(lǐng)域前沿項目等項目的資助,。(生物谷Bioon.com)
doi:10.1042/BJ20121493
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PMID:
Human cytoplasmic ProX edits mischarged tRNAPro with amino acid but not tRNA specificity
Liang-Liang Ruan, Xiao-Long Zhou, Min Tan and En-Duo Wang
Aminoacyl-tRNA synthetases (aaRSs) are responsible for ensuring the fidelity of the genetic code translation by accurately linking a particular amino acid to its cognate tRNA isoacceptor. To ensure accuracy of protein biosynthesis, some aaRSs have evolved an editing process to remove mischarged tRNA. The hydrolysis of the mischarged tRNA usually occurs in an editing domain, which is inserted into or appended to the main body of the aaRS. In addition, autonomous, editing domain-homologous proteins can also trans-edit mischarged tRNA in concert or in compensating for the editing function of its corresponding aaRS. The freestanding ProX is a homologue of the editing domain of bacterial ProRS. In the present work, we cloned for the first time a gene encoding the human cytoplasmic ProX (HsProX) and purified the expressed recombinant protein. The catalytic specificity of HsProX for non-cognate amino acids and identity elements on tRNAPro for editing were also investigated. We found that HsProX could deacylate mischarged Ala-tRNAPro, but not Cys-HstRNAPro (UGG), and specifically targeted the Ala moiety of Ala-tRNAPro. The importance of the CCA76 end of the tRNA for deacylation activity and key amino acid residues in HsProX for its editing function were also identified.
