An mRNA structure in bacteria that controls gene expression by binding lysine

Riboswitches are metabolite-responsive genetic control elements that reside in the untranslated regions (UTRs) of certain messenger RNAs. Herein, we report that the 5'-UTR of the lysC gene of Bacillus subtilis carries a conserved RNA element that serves as a lysine-responsive riboswitch. The ligand-binding domain of the riboswitch binds to L-lysine with an apparent dissociation constant (K-D) of similar to1 muM, and exhibits a high level of molecular discrimination against closely related analogs, including D-lysine and ornithine. Furthermore, we provide evidence that this widespread class of riboswitches serves as a target for the antimetabolite S-(2-aminoethyl)-L-cysteine (AEC). These findings add support to the hypotheses that direct sensing of metabolites by messenger RNAs is a fundamental form of genetic control and that riboswitches represent a new class of antimicrobial drug targets.