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Nucleic Acids Research Advance Access published online on August 28, 2007
Nucleic Acids Research, doi:10.1093/nar/gkm633
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© 2007 The Author(s)
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Nucleic Acid Enzymes

Human tryptophanyl-tRNA synthetase is switched to a tRNA-dependent mode for tryptophan activation by mutations at V85 and I311

Li-Tao Guo1, Xiang-Long Chen1, Bo-Tao Zhao1, Yi Shi1, Wei Li1, Hong Xue2 and You-Xin Jin1,*

1State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 320 Yue-Yang Road, Shanghai 200031 and 2Department of Biochemistry, Hong Kong University of Science and Technology, Clear Water Bay, Kwoloon, Hong Kong, China

*To whom correspondence should be addressed. Tel: 0086 21 54921222; Fax: 0086 21 5492 1011; Email: yxjin{at}sibs.ac.cn

Received April 28, 2007. Revised August 2, 2007. Accepted August 2, 2007.

For most aminoacyl-tRNA synthetases (aaRS), their cognate tRNA is not obligatory to catalyze amino acid activation, with the exception of four class I (aaRS): arginyl-tRNA synthetase, glutamyl-tRNA synthetase, glutaminyl-tRNA synthetase and class I lysyl-tRNA synthetase. Furthermore, for arginyl-, glutamyl- and glutaminyl-tRNA synthetase, the integrated 3' end of the tRNA is necessary to activate the ATP-PPi exchange reaction. Tryptophanyl-tRNA synthetase is a class I aaRS that catalyzes tryptophan activation in the absence of its cognate tRNA. Here we describe mutations located at the appended ß1–ß2 hairpin and the AIDQ sequence of human tryptophanyl-tRNA synthetase that switch this enzyme to a tRNA-dependent mode in the tryptophan activation step. For some mutant enzymes, ATP-PPi exchange activity was completely lacking in the absence of tRNATrp, which could be partially rescued by adding tRNATrp, even if it had been oxidized by sodium periodate. Therefore, these mutant enzymes have strong similarity to arginyl-tRNA synthetase, glutaminyl-tRNA synthetase and glutamyl-tRNA synthetase in their mode of amino acid activation. The results suggest that an aaRS that does not normally require tRNA for amino acid activation can be switched to a tRNA-dependent mode.


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N. Shen, M. Zhou, B. Yang, Y. Yu, X. Dong, and J. Ding
Catalytic mechanism of the tryptophan activation reaction revealed by crystal structures of human tryptophanyl-tRNA synthetase in different enzymatic states
Nucleic Acids Res., March 27, 2008; 36(4): 1288 - 1299.
[Abstract] [Full Text] [PDF]


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