Stepan Ovchinnikov, Konstantin Gilep, Konstantin Severinov and Svetlana Dubiley have co-authored a paper “GNAT toxins evolve toward narrow tRNA target specificities” that has been recently published in Nucleic Acids Research. Type II toxin–antitoxin (TA) systems are two-gene modules widely distributed among prokaryotes. GNAT toxins associated with the DUF1778 antitoxins represent a large family of type II TAs. The scientists explored the evolutionary trajectory of GNAT toxins. They systematically investigated the in vivo substrate specificity of an array of diverse GNAT toxins. Our functional data show that the majority of GNAT toxins are specific to Gly-tRNA isoacceptors. The phylogenetic analysis shows that the ancestor of GNAT toxins was likely a relaxed specificity enzyme capable of acetylating multiple elongator tRNAs. Full text of the paper is available here.