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Publication Abstract from PubMed

To ensure a high fidelity during translation, threonyl-tRNA synthetases (ThrRSs) harbor an editing domain that removes noncognate L-serine attached to tRNAThr. Most archaeal ThrRSs possess a unique editing domain structurally similar to D-aminoacyl-tRNA deacylases (DTDs) found in eubacteria and eukaryotes that specifically removes D-amino acids attached to tRNA. Here, we provide mechanistic insights into the removal of noncognate L-serine from tRNAThr by a DTD-like editing module from Pyrococcus abyssi ThrRS (Pab-NTD). High-resolution crystal structures of Pab-NTD with pre- and post-transfer substrate analogs and with L-serine show mutually nonoverlapping binding sites for the seryl moiety. Although the pre-transfer editing is excluded, the analysis reveals the importance of main chain atoms in proper positioning of the post-transfer substrate for its hydrolysis. A single residue has been shown to play a pivotal role in the inversion of enantioselectivity both in Pab-NTD and DTD. The study identifies an enantioselectivity checkpoint that filters opposite chiral molecules and thus provides a fascinating example of how nature has subtly engineered this domain for the selection of chiral molecules during translation.

Post-transfer editing mechanism of a D-aminoacyl-tRNA deacylase-like domain in threonyl-tRNA synthetase from archaea.,Hussain T, Kruparani SP, Pal B, Dock-Bregeon AC, Dwivedi S, Shekar MR, Sureshbabu K, Sankaranarayanan R EMBO J. 2006 Sep 6;25(17):4152-62. Epub 2006 Aug 10. PMID:16902403^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.