The structure of a tetrahydrofolate-sensing riboswitch reveals two ligand binding sites in a single aptamer.

ABSTRACT: Transport and biosynthesis of folate and its derivatives are frequently controlled by the tetrahydrofolate (THF) riboswitch in Firmicutes. We have solved the crystal structure of the THF riboswitch aptamer in complex with folinic acid, a THF analog. Uniquely, this structure reveals two molecules of folinic acid binding to a single structured domain. These two sites interact with ligand in a similar fashion, primarily through recognition of the reduced pterin moiety. 7-deazaguanine, a soluble analog of guanine, binds the riboswitch with nearly the same affinity as its natural effector. However, 7-deazaguanine effects transcriptional termination to a substantially lesser degree than folinic acid, suggesting that the cellular guanine pool does not act upon the THF riboswitch. Under physiologi

SUBMITTER: Trausch JJ 

PROVIDER: S-EPMC3196276 | biostudies-literature | 2011 Oct

REPOSITORIES: biostudies-literature