Coexistence of bacterial leucyl-tRNA synthetases with archaeal tRNA binding domains that distinguish tRNA(Leu) in the archaeal mode.
Leucyl-tRNA (transfer RNA) 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(Leu)s. The tRNA recognition mode, aminoacylation and translational quality control activities of these two LeuRSs are interesting questions to be addressed. Herein, active NmLeuRS1 and NmLeuRS2 were successfully purified after gene expression in Escherichia coli. Under the optimized aminoacylation conditions, we discovered that they 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, we demonstrated misactivation 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 aminoacyl-tRNA synthetases and tRNA.
Center for RNA Research, State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, The Chinese Academy of Sciences, 320 Yue Yang Road, Shanghai 200031, China.
Zhi-Peng
ZP
Fang
Meng
M
Wang
Zhi-Rong
ZR
Ruan
Min
M
Tan
Ru-Juan
RJ
Liu
Mi
M
Zhou
Xiao-Long
XL
Zhou
En-Duo
ED
Wang
D000596:Amino Acids / Q000378:metabolism; D001419:Bacteria / Q000201:enzymology; D006216:Halobacteriaceae / Q000201:enzymology* / Q000235:genetics; D006863:Hydrogen-Ion Concentration; D007935:Leucine-tRNA Ligase / Q000737:chemistry / Q000145:classification / Q000378:metabolism*; D011189:Potassium Chloride; D017434:Protein Structure, Tertiary; D012356:RNA, Transfer, Leu / Q000378:metabolism*; D046249:Transfer RNA Aminoacylation
D000596:Amino Acids; D012356:RNA, Transfer, Leu; D011189:Potassium Chloride; D007935:Leucine-tRNA Ligase