Fig. 1From: Engineering a vitamin B12 high-throughput screening system by riboswitch sensor in Sinorhizobium melilotiMechanism 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 expressionBack to article page