4.18.4.4. Mechanisms of riboswitches

iboswitches are often conceptually divided into two parts: an Aptamer and an expression platform. The aptamer directly binds the small molecule, and the expression platform undergoes structural changes in response to the changes in the aptamer. The expression platform is what regulates gene expression. Expression platforms typically turn off gene expression in response to the small molecule, but some turn it on. The following riboswitch mechanisms have been experimentally demonstrated.

• Riboswitch-controlled formation of rho-independent transcription termination hairpins leads to premature transcription termination.
• Riboswitch-mediated folding sequesters the ribosome-binding site, thereby inhibiting translation.
• The riboswitch is a ribozyme that cleaves itself in the presence of sufficient concentrations of its metabolite.
• Riboswitch alternate structures affect the splicing of the pre-mRNA.
• A riboswitch in Clostridium acetobutylicum regulates an adjacent gene that is not part of the same mRNA transcript.
• A riboswitch in Listeria monocytogenes regulates the expression of its downstream gene.

4.18.4.4. Genetic Control Mechanisms - RIBOSWITCHES

4.18.4.5. Other Functional Mechanism
(a)Transcription Control termination and anti-termination, (b) Translation initiation: RBS accessibility, (c) RNA processing: Splicing or degradation

4.18.4.6. Crystal structure of Some Riboswitch