近期Nucleic Acids Research在線發表了上海生化與細胞所王恩多研究組的研究論文：人細胞質亮氨醯-tRNA合成酶編校非對應胺基酸的模塊式途徑。
為了防止潛在的蛋白質錯誤合成，某些氨基醯-tRNA合成酶具有編校功能去除錯誤活化的胺基酸或者錯誤接載的氨基醯化tRNA，通過控制蛋白質的生物合成原料的質量，對蛋白質合成進行質量控制。該實驗室已經證明亮氨醯-tRNA合成酶(LeuRS)能夠通過不依賴-或依賴tRNA轉移前編校途徑水解誤活化的非對應胺基酸，即使誤活化的胺基酸轉移到tRNA分子上也可以通過轉移後編校途徑將其水解。 LeuRS通過多條編校途徑在反應的各個步驟清除錯誤的反應產物和中間物。
王恩多研究組的博士研究生陳鑫和馬晶晶成功地首次在大腸桿菌基因表達體系中得到了高活力的人胞質亮氨醯-tRNA合成酶(hcLeuRS)和亮氨酸tRNA，建立了一個高效的測定hcLeuRS合成和編校活力方法和體外研究體系。發現hcLeuRS對不同的非對應胺基酸的脅迫採取不同的編校策略對產物進行質量控制，雖然亮氨酸的類似物正纈氨酸(Nva)和2-氨基丁酸(ABA)都能被錯誤地載入tRNA分子的3』端，但主要通過轉移後的編校途徑去除Nva，去除ABA則偏愛轉移前的編校途徑。轉移後編校作為tRNA氨基醯化最後的一個質量控制的檢查點對於避免胺基酸的錯誤摻入發揮著至關重要的作用。該研究結果將有助於更加深入、全面地認識生物進化過程中產生的模塊式編校途徑在保持遺傳信息由RNA傳遞到蛋白質的精確性發揮著重要作用。
該研究得到中國科學院，科技部重大科學研究計劃，國家自然科學基金委，上海市科委的資助。（生物谷Bioon.com）
生物谷推薦英文摘要：
Nucleic Acids Research, doi:10.1093/nar/gkq763
Modular pathways for editing non-cognate amino acids by human cytoplasmic leucyl-tRNA synthetase
Xin Chen1, Jing-Jing Ma1, Min Tan1, Peng Yao1, Qing-Hua Hu1, Gilbert Eriani2 and En-Duo Wang1,*
1State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Graduate School of the Chinese Academy of Sciences, The Chinese Academy of Sciences, 320 Yue Yang Road, Shanghai 200031, China and 2Architecture et Réactivité de l』ARN, Institut de Biologie Moléculaire et Cellulaire du CNRS, Université de Strasbourg, 15 rue René Descartes 67084 Strasbourg, France
To prevent potential errors in protein synthesis, some aminoacyl-transfer RNA (tRNA) synthetases have evolved editing mechanisms to hydrolyze misactivated amino acids (pre-transfer editing) or misacylated tRNAs (post-transfer editing). Class Ia leucyl-tRNA synthetase (LeuRS) may misactivate various natural and non-protein amino acids and then mischarge tRNALeu. It is known that the fidelity of prokaryotic LeuRS depends on multiple editing pathways to clear the incorrect intermediates and products in the every step of aminoacylation reaction. Here, we obtained human cytoplasmic LeuRS (hcLeuRS) and tRNALeu (hctRNALeu) with high activity from Escherichia coli overproducing strains to study the synthetic and editing properties of the enzyme. We revealed that hcLeuRS could adjust its editing strategy against different non-cognate amino acids. HcLeuRS edits norvaline predominantly by post-transfer editing; however, it uses mainly pre-transfer editing to edit -amino butyrate, although both amino acids can be charged to tRNALeu. Post-transfer editing as a final checkpoint of the reaction was very important to prevent mis-incorporation in vitro. These results provide insight into the modular editing pathways created to prevent genetic code ambiguity by evolution.