A Chiral Selectivity Relaxed Paralog Of DTD For Proofreading tRNA Mischarging In Animalia

Abstract

D-aminoacyl-tRNA deacylase (DTD), a trans-editing factor found in bacteria and eukaryotes, removes D-amino acids mischarged on tRNAs as well as achiral glycine mischarged on tRNAAla. An invariant cross-subunit Gly-cisPro motif forms the mechanistic basis of strict L-amino acid rejection from the catalytic site. Here, we present the identification of a DTD variant, named ATD (Animalia-specific tRNA deacylase), that harbors a Gly-transPro motif. The cis-to-trans switch causes a \"gain of function\" through L-chiral selectivity in ATD resulting in the clearing of L-alanine mischarged on tRNAThr(G4*U69) by eukaryotic AlaRS. The biochemical proofreading activity of ATD is conserved across diverse classes of phylum Chordata. Animalia genomes enriched in tRNAThr(G4*U69) genes are in strict association with the presence of ATD, underlining the mandatory requirement of a dedicated factor to proofread tRNA misaminoacylation. The study highlights the emergence of ATD during genome expansion as a key event associated with the evolution of Animalia.