PreQ1-II riboswitches form a class of riboswitches that specifically bind pre-queuosine1 (PreQ1), a precursor of the modified nucleoside queuosine.

[1] They are found in certain species of Streptococcus and Lactococcus, and were originally identified as a conserved RNA secondary structure called the "COG4708 motif".

These genes are predicted to encode membrane-bound proteins and have been proposed to be a transporter of preQ1, or a related metabolite, based on their association with preQ1-binding riboswitches.

PreQ1 thus joins S-adenosylmethionine as the second metabolite to be found that is the ligand of more than one riboswitch class.

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