Figure 1

Typical activating riboswitch function. A ribosome binding site (RBS, purple) is sequestered within a riboswitch preventing ribosome recruitment. (A) A standard riboswitch in which binding of a ligand (yellow) causes a conformational change exposing the RBS, allowing translation of the gene of interest (blue). (B) A ribo-attenuator adds a second RBS, sequestered away by a local hairpin. The hairpin can be opened by a ribosome travelling from the riboswitch RBS, exposing the attenuator RBS and allowing translation of the gene of interest. Dynamic operation of both systems is further explained in our video animation⁵³.