btuB riboswitch

The btuB riboswitch is a cis-regulatory RNA element located in the 5' untranslated region (UTR) of the btuB mRNA, primarily characterized in Escherichia coli and other Gram-negative bacteria (Nahvi et al., 2002). It serves as a high-affinity sensor for adenosylcobalamin (AdoCbl), a coenzyme form of vitamin B12, regulating the expression of the btuB gene which encodes an outer membrane cobalamin transporter (Cadreux et al., 2022). Upon binding AdoCbl, the riboswitch undergoes a structural rearrangement that sequesters the Shine-Dalgarno sequence, thereby inhibiting translation initiation through an "off-switch" mechanism (Nahvi et al., 2004). This regulatory process is vital for maintaining cellular homeostasis of vitamin B12 and preventing the energetic cost of unnecessary transporter synthesis. Because riboswitches are highly specific to bacteria and regulate essential metabolic pathways, they are increasingly investigated as targets for novel antimicrobial agents, such as cobalamin analogs that can constitutively trigger gene repression (Blount and Breaker, 2006).

Other names

Cobalamin riboswitchVitamin B12 riboswitchAdoCbl riboswitchB12-element

Ligand binding to the aptamer domain induces a conformational change in the expression platform, sequestering the ribosome binding site to inhibit translation (Nahvi et al., 2004).