SAM–SAH riboswitch
The SAM–SAH riboswitch is a conserved RNA structure in certain bacteria that binds S-adenosylmethionine (SAM) and S-adenosylhomocysteine (SAH) and is therefore presumed to be a riboswitch. SAM–SAH riboswitches do not share any apparent structural resemblance to known riboswitches that bind SAM or SAH. The binding affinities for both compounds are similar, but binding for SAH is at least somewhat stronger.