State Key Laboratory of Molecular Biology, Shanghai Institutes for Biological Sciences, The Chinese Academy of Sciences, Shanghai, China.
Biochem J. 2012 Apr 15;443(2):477-84. doi: 10.1042/BJ20111925.
aaRSs (aminoacyl-tRNA synthetases) establish the rules of the genetic code by catalysing the formation of aminoacyl-tRNA. The quality control for aminoacylation is achieved by editing activity, which is usually carried out by a discrete editing domain. For LeuRS (leucyl-tRNA synthetase), the CP1 (connective peptide 1) domain is the editing domain responsible for hydrolysing mischarged tRNA. The CP1 domain is universally present in LeuRSs, except MmLeuRS (Mycoplasma mobile LeuRS). The substitute of CP1 in MmLeuRS is a nonapeptide (MmLinker). In the present study, we show that the MmLinker, which is critical for the aminoacylation activity of MmLeuRS, could confer remarkable tRNA-charging activity on the inactive CP1-deleted LeuRS from Escherichia coli (EcLeuRS) and Aquifex aeolicus (AaLeuRS). Furthermore, CP1 from EcLeuRS could functionally compensate for the MmLinker and endow MmLeuRS with post-transfer editing capability. These investigations provide a mechanistic framework for the modular construction of aaRSs and their co-ordination to achieve catalytic efficiency and fidelity. These results also show that the pre-transfer editing function of LeuRS originates from its conserved synthetic domain and shed light on future study of the mechanism.
aaRSs（氨酰-tRNA 合成酶）通过催化氨酰-tRNA 的形成来确定遗传密码的规则。氨酰化的质量控制是通过编辑活性来实现的，通常由离散的编辑结构域来完成。对于 LeuRS（亮氨酰-tRNA 合成酶），CP1（连接肽 1）结构域是负责水解错误负载 tRNA 的编辑结构域。CP1 结构域普遍存在于 LeuRS 中，除了 MmLeuRS（Mycoplasma mobile LeuRS）。MmLeuRS 中的 CP1 替代物是一个九肽（MmLinker）。在本研究中，我们表明，MmLinker 对 MmLeuRS 的氨酰化活性至关重要，它可以赋予无活性的 CP1 缺失的大肠埃希菌（EcLeuRS）和水生栖热菌（Aquifex aeolicus）LeuRS（AaLeuRS）显著的 tRNA 负载活性。此外，EcLeuRS 的 CP1 可以在功能上补偿 MmLinker，并赋予 MmLeuRS 转移后编辑能力。这些研究为 aaRSs 的模块化构建及其协调以实现催化效率和保真度提供了一个机制框架。这些结果还表明，LeuRS 的转移前编辑功能源于其保守的合成结构域，并为未来的机制研究提供了线索。
