title: Tetracycline determines the conformation of its aptamer at physiological magnesium concentrations.
abstract: Synthetic riboswitches are versatile tools for the study and manipulation of biological systems. Yet, the underlying mechanisms governing its structural properties and regulation under physiological conditions are poorly studied. We performed spectroscopic and calorimetric experiments to explore the folding kinetics and thermodynamics of the tetracycline-binding aptamer, which can be employed as synthetic riboswitch, in the range of physiological magnesium concentrations. The dissociation constant of the ligand-aptamer complex was found to strongly depend on the magnesium concentration. At physiological magnesium concentrations, tetracycline induces a significant conformational shift from a compact, but heterogeneous intermediate state toward the completely formed set of tertiary interactions defining the regulation-competent structure. Thus, the switching functionality of the tetracycline-binding aptamer appears to include both a conformational rearrangement toward the regulation-competent structure and its thermodynamic stabilization.
authors.affiliation: Institute of Physical and Theoretical Chemistry, Goethe University Frankfurt am Main, Frankfurt, Germany.
authors.forename: Andreas J
authors.initials: AJ
authors.lastname: Reuss
authors.affiliation: Department of Biology, Technical University of Darmstadt, Darmstadt, Germany.
authors.forename: Marc
authors.initials: M
authors.lastname: Vogel
authors.affiliation: Department of Biology, Technical University of Darmstadt, Darmstadt, Germany.
authors.forename: Julia E
authors.initials: JE
authors.lastname: Weigand
authors.affiliation: Department of Biology, Technical University of Darmstadt, Darmstadt, Germany. Electronic address: bsuess@bio.tu-darmstadt.de.
authors.forename: Beatrix
authors.initials: B
authors.lastname: Suess
authors.affiliation: Institute of Physical and Theoretical Chemistry, Goethe University Frankfurt am Main, Frankfurt, Germany. Electronic address: wveitl@theochem.uni-frankfurt.de.
authors.forename: Josef
authors.initials: J
authors.lastname: Wachtveitl
mesh_terms: D000900:Anti-Bacterial Agents / Q000737:chemistry*; D001483:Base Sequence; D008274:Magnesium / Q000737:chemistry*; D008969:Molecular Sequence Data; D012313:RNA / Q000737:chemistry*; D013752:Tetracycline / Q000737:chemistry*
chemical_list: D000900:Anti-Bacterial Agents; D012313:RNA; D013752:Tetracycline; D008274:Magnesium