Riboswitches are a rather elegant way to regulate gene expression without any additional machinery. A small ligand binds to the mRNA and directly influences transcription or translation.

Most of the known riboswitches are found in bacteria, there are few examples of riboswitches in eukaryotes. There are no classical riboswitches in humans as far as I know (there is one example, but triggered by a protein and not a metabolite), it seems that more complex organisms tend to use other methods of gene regulation.

Are there any known reasons for this? What are the drawbacks of regulating gene expression with riboswitches compared to using regulatory proteins? Is there an explanation for the lack of riboswitches in more complex organisms?


1 Answer 1


You get higher accuracy and more timely control at a post translational level (think about the time it takes to affect a pathway with cofactor stimulation compared to gene expression stimulation). You also have more points of control throughout the pathway if you affect activity post translationally allowing for a more complex interaction between stimulating and repressing factors.

  • $\begingroup$ This may or may not be true. However it doesn't answer the question of "why bacteria and not eukaryotes?" $\endgroup$
    – David
    Commented Aug 18, 2017 at 20:41

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