New Study Provides Insight into the Mechanism of Bacterial Leucyl-tRNA Synthetase

During the evolution，aminoacyl-tRNA synthetases (aaRSs) progressively recruit domains and motifs for effective and accurate aminoacylation. The leucine-specific domain (LSD) is a compact, well-ordered module that participates in positioning of the conserved KMSKS catalytic loop in most leucyl-tRNA synthetases (LeuRSs). Now a new study from Chinese Academy of Sciences provides new insight into the modulation of Aminoacylation and Proofreading Functional Cycle of LeuRSs.

Compared to the universal present aminoacylation domain, editing domain and tRNA binding domain of LeuRS, LSD is absent in some LeuRSs, including those from Bacillus subtilis and Mycoplasma. LeuRS from Mycoplasma mobile (MmLeuRS), which is the only naturally CP1-deprived LeuRS, has a tetrapeptide GKDG instead of the LSD. Ms. YAN Wei, Dr. TAN Min and their colleagues led by Professor WANG Enduo from Shanghai Institute of Biochemistry and Cell Biology, CAS show that the tetrapeptide GKDG can confer tRNA charging and post-transfer editing activity when transplanted into an inactive Escherichia coli LeuRS (EcLeuRS) that has had its LSD deleted. Reciprocally, the LSD, together with the CP1 editing domain of EcLeuRS, can cooperate when inserted into the scaffold of the minimal MmLeuRS, and this generates an enzyme nearly as active as EcLeuRS.

Further, they show that LSD participates in tRNA^Leu recognition and favors the binding of tRNAs harboring a large loop in the variable-arm. Additional analysis established that the Lys598 of the LSD is the critical residue for tRNA recognition. Conversion of Lys598 to Ala simultaneously reduces the tRNA binding strength, aminoacylation and editing capacities, indicating that these factors are subtly connected and controlled at the level of the LSD. The present work provides a novel framework of co-evolution between LeuRS and its cognate tRNA through LSD.

This work entitled “Leucine-Specific Domain (LSD) Modulates the Aminoacylation and Proofreading Functional Cycle of Bacterial Leucyl-tRNA Synthetase” was published online in Nucleic Acids Research on March 21^st. It is funded by grants from the Ministry of Science and Technology of China, the National Natural Science Foundation of China, CAS, and the Science and Technology Commission of Shanghai Municipality.

Cloverleaf structure of tRNA^Leu and tertiary structure of Leucine-Specific Domain investigated in this study (Image provided by Prof. WANG Enduo)