Leucyl-tRNA synthetase (LeuRS) is a multi-domain enzyme that catalyzes Leu-tRNALeu formation, providing materials for protein synthesis. LeuRS could be classified into bacterial and archaeal/eukaryotic types. Both types of LeuRS possess a catalytic domain (for amino acid activation and tRNA charging), a CP1 domain (for editing), an α-helix bundle domain and a C-teminal domain (CTD, for tRNA binding). CTDs of both bacterial and archaeal LeuRSs have been reported to recognize tRNALeu through different modes of interaction, for the primary sequence and tertiary structure is different.
Candida albicans, a human opportunistic pathogen, has evolved a chimeric CatRNASer(CAG) which could be recognized by Candida albicans seryl-tRNA synthetase (CaSerRS) to form Ser-tRNASer and by Candida albicans LeuRS (CaLeuRS) to form Leu-tRNASer, leading to the universal Leu codon CUG deciphered as both Ser (97%) and Leu (3%). This resultant ambiguity at the CTG codon is crucial in the morphological switch and virulence of this pathogen. The elements in CaSerRS that recognize tRNASer has been revealed, however, that in CaLeuRS is unknown. Besides CaLeuRS, homo sapiens LeuRS and Saccharomyces cerevisiae LeuRS also could aminoacylate CatRNASer(CAG), but other types couldn’t (including Candida albicans mitochondrial LeuRS, Pyrococcus horikoshii LeuRS and Escherichia coli LeuRS). The most difference between eukaryotic and archaeal LeuRS is their highly divergent CTD, suggesting its potential role in tRNASer recognition.
Recently, graduate students JI Quanquan et al, under the guidance of Professor WANG Enduo and Dr. ZHOU Xiaolong, at the Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, CAS, identified that CTD of CaLeuRS (CaCTD) is indispensible for leucylating both CatRNASer(CAG) and CatRNALeu (CatRNAs). Truncation of the terminal five residues makes the leucylation activity of the enzyme totally lost. Additionally, three highly conserved lysine residues within CaCTD were identified as important for leucylating both tRNAs in an additive manner. The importance of the three lysine residues was further verified by gel mobility shift assays and complementation of a yeast leuS gene knockout strain. In combination, They identified the specific mechanism concerning recognition of CatRNASer(CAG) by CaLeuRS and improved the understanding of the recognition of tRNALeu by eukaryotic LeuRS.
This work, entitled “C-terminal domain of leucyl-tRNA synthetase from pathogenicCandida albicansrecognizes both tRNASerand tRNALeu”, was published online in Journal of Biological Chemistry on December 16, 2015 and was supported by grants from the NSFC, MOST, CAS and STCSM.
AUTHOR CONTACT:
WANG Enduo
Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, Shanghai, China
Phone: 86-21-54921241;
E-mail: edwang@sibcb.ac.cn
Three lysines affect the tRNA-binding capacity of CaLeuRS
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