A flexizyme that selectively charges amino acids activated by a water-friendly leaving group

We have developed a new flexizyme (a flexible de novo tRNA acylation ribozyme) system, a pair of amino-derivatized benzyl thioester (ABT) and amino flexizyme (aFx). ABT bearing the ammonium ion was designed to render the acyl-donor substrates better water solubility. Although the previously reported flexizymes (eFx and dFx) did not show acylation activity for the ABT derivatives, a new flexizyme variant aFx, generated by in vitro selection against an amino acid activated ABT, exhibits high selectivity toward those activated ABT. The flexizymes system including aFx, eFx, and dFx enables us to prepare a wide variety of acyl-tRNAs charged with non-proteinogenic amino acids.