Role of D-aminoacyl-tRNA deacylase beyond chiral proofreading as a cellular defense against glycine mischarging by AlaRS

• Published in: eLife Vol. 6
• Main Authors: Pawar, Komal Ishwar, Suma, Katta, Seenivasan, Ayshwarya, Kuncha, Santosh Kumar, Routh, Satya Brata, Kruparani, Shobha P, Sankaranarayanan, Rajan
• Format: Journal Article
• Language: English
• Published: England eLife Sciences Publications Ltd 31.03.2017; eLife Sciences Publications, Ltd
• Subjects: Alanine; Alanine-tRNA Ligase - antagonists & inhibitors; Amino acids; Aminoacyltransferases - metabolism; Apoptosis; Biochemistry; Biophysics and Structural Biology; chirality; D-Amino acids; E coli; Editing; Escherichia coli - enzymology; Escherichia coli - metabolism; genetic code; Glycine; Glycine - metabolism; Proteins; Toxicity; translation; tRNA; tRNA synthetase; chirality; amino acids; biochemistry; translation; structural biology; tRNA synthetase; biophysics; E. coli; genetic code
• ISSN: 2050-084X; 2050-084X
• DOI: 10.7554/eLife.24001

Strict L-chiral rejection through Gly- Pro motif during chiral proofreading underlies the inability of D-aminoacyl-tRNA deacylase (DTD) to discriminate between D-amino acids and achiral glycine. The consequent Gly-tRNA 'misediting paradox' is resolved by EF-Tu in the cell. Here, we show that DTD's active site architecture can efficiently edit mischarged Gly-tRNA 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 even at low-glycine levels which is alleviated by alanine supplementation. We further demonstrate that DTD positively selects the universally invariant tRNA -specific G3•U70. Moreover, DTD's activity on non-cognate Gly-tRNA 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.