Jakubowski H, Fersht A R
Nucleic Acids Res. 1981 Jul 10;9(13):3105-17. doi: 10.1093/nar/9.13.3105.
Evidence is presented that the editing mechanisms of aminoacyl-tRNA synthetase operate by two alternative pathways: pre-transfer, by hydrolysis of the non-cognate aminoacyl adenylate; post-transfer, by hydrolysis of the mischarged tRNA. The methionyl-tRNA synthetases from Escherichia coli and Bacillus stearothermophilus and isoleucyl-tRNA synthetase from E. coli, for example, are shown to reject misactivated homocysteine rapidly by the pre-transfer route. A novel feature of this reaction is that homocysteine thiolactone is formed by the facile cyclisation of the homocysteinyl adenylate. Valyl-tRNA synthetases, on the other hand, reject the more readily activated non-cognate amino acids by primarily the post-transfer route. The features governing the choice of pathway are discussed.
有证据表明，氨酰-tRNA合成酶的编辑机制通过两种替代途径起作用：转移前，通过水解非同源氨酰腺苷酸；转移后，通过水解错配的tRNA。例如，来自大肠杆菌和嗜热栖热芽孢杆菌的甲硫氨酰-tRNA合成酶以及来自大肠杆菌的异亮氨酰-tRNA合成酶，显示出通过转移前途径快速排斥错误激活的同型半胱氨酸。该反应的一个新特点是，同型半胱氨酰腺苷酸通过容易的环化作用形成同型半胱氨酸硫内酯。另一方面，缬氨酰-tRNA合成酶主要通过转移后途径排斥更容易激活的非同源氨基酸。讨论了决定途径选择的特征。
