title: A disconnect between high-affinity binding and efficient regulation by antifolates and purines in the tetrahydrofolate riboswitch.
abstract: The tetrahydrofolate (THF) riboswitch regulates folate transport and metabolism in a number of Firmicutes by cooperatively binding two molecules of THF. To further understand this riboswitch's specificity for THF, binding and regulatory activity of a series of THF analogs and antifolates were examined. Our data reveal that although binding is dominated by the RNA's interactions with the pterin moiety, the para-aminobenzoic acid (pABA) moiety plays a significant role in transcriptional regulation. Further, we find that adenine and several other analogs bind with high affinity by an alternative binding mechanism. Despite a similar affinity to THF, adenine is a poor regulator of transcriptional attenuation. These results demonstrate that binding alone does not determine a compound's effectiveness in regulating the activity of the riboswitch-a complication in current efforts to develop antimicrobials that target these RNAs.
authors.affiliation: Department of Chemistry and Biochemistry, University of Colorado at Boulder, Campus Box 596, Boulder, CO 80309-0596, USA.
authors.forename: Jeremiah J
authors.initials: JJ
authors.lastname: Trausch
authors.affiliation: Department of Chemistry and Biochemistry, University of Colorado at Boulder, Campus Box 596, Boulder, CO 80309-0596, USA. Electronic address: robert.batey@colorado.edu.
authors.forename: Robert T
authors.initials: RT
authors.lastname: Batey
mesh_terms: D000225:Adenine / Q000737:chemistry / Q000378:metabolism; D001665:Binding Sites; D005493:Folic Acid Antagonists / Q000737:chemistry / Q000378:metabolism*; D002955:Leucovorin / Q000737:chemistry / Q000378:metabolism; D008727:Methotrexate / Q000737:chemistry / Q000378:metabolism; D062105:Molecular Docking Simulation; D009690:Nucleic Acid Conformation; D011687:Purines / Q000737:chemistry / Q000378:metabolism*; D058928:Riboswitch; D013763:Tetrahydrofolates / Q000737:chemistry / Q000378:metabolism*; D061806:Transcription Termination, Genetic
chemical_list: D005493:Folic Acid Antagonists; D011687:Purines; D058928:Riboswitch; D013763:Tetrahydrofolates; C030371:5,6,7,8-tetrahydrofolic acid; D000225:Adenine; D002955:Leucovorin; D008727:Methotrexate