Aminoacylation of Proteins: New Targets for the Old ARSenal

Besides charging tRNAs with their cognate amino acids, aminoacyl-tRNA synthetases (ARSs) are involved in a plethora of non-canonical functions, including development, immune response, and angiogenesis. In this issue of Cell Metabolism , He et al. (2018) report a novel biochemical function of ARSs: posttranslational addition of amino acids to lysine residues in proteins.