Role of D-aminoacyl-tRNA deacylase beyond chiral proofreading as a cellular defense against glycine mischarging by AlaRS
Abstract
Strict L-chiral rejection through Gly-cisPro motif during chiral proofreading underlies inability of D-aminoacyl-tRNA deacylase (DTD) to discriminate between D-amino acids and achiral glycine. The consequent Gly-tRNAGly 'misediting paradox' is resolved by EF-Tu in the cell. Here, we show that DTD’s active site architecture can efficiently edit mischarged Gly-tRNAAla species four orders of magnitude more efficiently than even AlaRS, the only ubiquitous cellular checkpoint known for clearing the error. Also, DTD knockout in AlaRS editing-defective background causes pronounced toxicity in Escherichia coli even at low glycine levels which is alleviated by alanine supplementation. We further demonstrate that DTD positively selects the universally invariant tRNAAla-specific G3•U70. Moreover, DTD’s activity on non-cognate Gly-tRNAAla is conserved across all bacteria and eukaryotes, suggesting DTD’s key cellular role as a glycine deacylator. Our study thus reveals a hitherto unknown function of DTD in cracking the universal mechanistic dilemma encountered by AlaRS, and its physiological importance.
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Funding
Council of Scientific and Industrial Research (12th Five Year Plan Project BSC0113)
- Rajan Sankaranarayanan
Science and Engineering Research Board (JC Bose Fellowship)
- Rajan Sankaranarayanan
Department of Biotechnology , Ministry of Science and Technology (Centre of Excellence)
- Rajan Sankaranarayanan
Council of Scientific and Industrial Research (Research Fellowship)
- Komal Ishwar Pawar
- Satya Brata Routh
Department of Biotechnology , Ministry of Science and Technology (Research Associateship)
- Katta Suma
Department of Biotechnology , Ministry of Science and Technology (INSPIRE Fellowship)
- Santosh Kumar Kuncha
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Copyright
© 2017, Pawar et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
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