title: 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 the 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-tRNAAlaspecies 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 inEscherichia colieven 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-tRNAAlais 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.
authors.affiliation: CSIR-Centre for Cellular and Molecular Biology, Hyderabad, India.
authors.forename: Komal Ishwar
authors.identifier: 0000-0002-1968-9851
authors.initials: KI
authors.lastname: Pawar
authors.affiliation: CSIR-Centre for Cellular and Molecular Biology, Hyderabad, India.
authors.forename: Katta
authors.initials: K
authors.lastname: Suma
authors.affiliation: CSIR-Centre for Cellular and Molecular Biology, Hyderabad, India.
authors.forename: Ayshwarya
authors.initials: A
authors.lastname: Seenivasan
authors.affiliation: CSIR-Centre for Cellular and Molecular Biology, Hyderabad, India.
authors.forename: Santosh Kumar
authors.initials: SK
authors.lastname: Kuncha
authors.affiliation: CSIR-Centre for Cellular and Molecular Biology, Hyderabad, India.
authors.forename: Satya Brata
authors.initials: SB
authors.lastname: Routh
authors.affiliation: CSIR-Centre for Cellular and Molecular Biology, Hyderabad, India.
authors.forename: Shobha P
authors.initials: SP
authors.lastname: Kruparani
authors.affiliation: CSIR-Centre for Cellular and Molecular Biology, Hyderabad, India.
authors.forename: Rajan
authors.identifier: 0000-0003-4524-9953
authors.initials: R
authors.lastname: Sankaranarayanan
mesh_terms: D000412:Alanine-tRNA Ligase / Q000037:antagonists & inhibitors*; D019881:Aminoacyltransferases / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology* / Q000378:metabolism*; D005998:Glycine / Q000378:metabolism*
chemical_list: D019881:Aminoacyltransferases; D000412:Alanine-tRNA Ligase; D005998:Glycine
keywords: E. coli; amino acids; biochemistry; biophysics; chirality; genetic code; structural biology; tRNA synthetase; translation