Fig. 1
![Fig. 1](http://media.springernature.com/full/springer-static/image/art%3A10.1186%2Fs12896-018-0441-2/MediaObjects/12896_2018_441_Fig1_HTML.gif)
Mechanism of riboswitch based intracellular vitamin B12. In the simplified example cells containing a very low concentration or none of the VB12 (green circle), the ribosome binding site (RBS) is unstructured. Under a higher concentration of target metabolite, the aptamer domain undergoes restructuring forming a hairloop to attenuate gene expression