The THF riboswitch, is a highly conserved RNA structure that was identified upstream of the folate transport and biosynthesis genes in Gram-positive bacteria from the Lactobacillales and Clostridiales orders . Folates are composed of three moieties: pterin, p-aminobenzoate, and glutamate. An active form of folate, tetrahydrofolate (THF), is an essential cofactor in one-carbon transfer reactions of central metabolism. De novo THF biosynthesis starts from GTP and proceeds in seven consecutive steps . Alternatively, Gram-positive bacteria salvage folate from the environment utilizing a unique ECF-type transport system composed of a folate-binding protein (FolT) and a common ECF module .
The RNA motif located in the leader region of folT gene in Alkaliphilus metalliredigens was demonstrated to serve as a THF-binding riboswitch [20659680