The interaction mechanism between leucyl-tRNA synthetases and tRNA^Leu in haloalkaliphile

On Feb 6, 2014, Nucleic Acids Research online published the work entitled “Coexistence of bacterial leucyl-tRNA synthetases with archaeal tRNA binding domains that distinguish tRNA^Leuin the archaeal mode” from Prof. Enduo Wang’s group in Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences.

Leucyl-tRNA synthetase (LeuRS) is a multi-domain enzyme, which is divided into bacterial and archaeal/eukaryotic types. In general, one specific LeuRS, the domains of which are of the same type, exists in a single cell compartment. However, some species, such as the haloalkaliphile Natrialba magadii, encode two cytoplasmic LeuRSs, NmLeuRS1 and NmLeuRS2, which are the first examples of naturally occurring chimeric enzymes with different domains of bacterial and archaeal types. Furthermore, N. magadii encodes typical archaeal tRNA^Leus. The tRNA recognition mode, aminoacylation and translational quality control activities of these two LeuRSs are interesting questions to be addressed.

FANG Zhi-Peng and his colleagues guided by Professor WANG En-Duo and Associate Professor ZHOU Xiao-Long successfully purified active NmLeuRS1 and NmLeuRS2 after gene expression in E. coli. They discovered that NmLeuRSs distinguished cognate NmtRNA^Leu in the archaeal mode, whereas the N-terminal region was of the bacterial type. However, NmLeuRS1 exhibited much higher aminoacylation and editing activity than NmLeuRS2, suggesting that NmLeuRS1 is more likely to generate Leu-tRNA^Leu for protein biosynthesis. Moreover, using NmLeuRS1 as a model, they demonstrated mis-activation of several non-cognate amino acids, and accuracy of protein synthesis was maintained mainly via post-transfer editing. This comprehensive study of the NmLeuRS/tRNA^Leu system provides a detailed understanding of the coevolution of aaRSs and tRNA, and the mechanism of aminoacyl-tRNA synthetase on quality control of protein biosynthesis in the haloalkaliphilic bacterium.

This study was supported by the National Basic Research Program of China, the Natural Science Foundation of China and the Chinese Academy of Sciences.

AUTHOR CONTACT:
WANG En-Duo
Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, the Chinese Academy of Sciences, Shanghai, China
Phone: 86-21-5492 1241;
E-mail: edwang@sibcb.ac.cn