Allosteric rearrangement of mRNA structure is mediated by ligand binding, and this results in modulation of gene expression.

In particular the metabolic flux of the tricarboxylic acid (TCA) cycle is effectively controlled by the riboswitch.

With lysine as an intracellular signal, the riboswitch regulates gene expression in response to specific metabolites.

The lysine riboswitch was first investigated in Bacilus subtilis, located at the 5’UTR of the lysC gene coding for aspartokinase.

[7] In both E. coli and Bacilus subtilis, the lysine riboswitch controls the production of citrate synthase, and therefore metabolic flux in the TCA cycle as decreases in citrate synthase activity contributes to increases in lysine production.