%0 Journal Article
%T Gly56 in the synthetic site of isoleucyl-tRNA synthetase confers specificity and maintains communication with the editing site.
%A Dulic M
%A Krpan N
%A Gruic-Sovulj I
%J FEBS Lett
%V 597
%N 24
%D 2023 12 28
%M 38015921
%F 3.864
%R 10.1002/1873-3468.14780
%X Isoleucyl-tRNA synthetase (IleRS) links isoleucine to cognate tRNA via the Ile-AMP intermediate. Non-cognate valine is often mistakenly recognized as the IleRS substrate; therefore, to maintain the accuracy of translation, IleRS hydrolyzes Val-AMP within the synthetic site (pre-transfer editing). As this activity is not efficient enough, Val-tRNAIle is formed and hydrolyzed in the distant post-transfer editing site. A strictly conserved synthetic site residue Gly56 was previously shown to safeguard Ile-to-Val discrimination during aminoacyl (aa)-AMP formation. Here, we show that the Gly56Ala variant lost its specificity in pre-transfer editing, confirming that this residue ensures the selectivity of all synthetic site reactions. Moreover, we found that the Gly56Ala mutation affects IleRS interaction with aa-tRNA likely by disturbing tRNA-dependent communication between the two active sites.