PMID: 22678284 , Related PDB ids: 3VRS, 4EN5, 4ENA, 4ENB, 4ENC

Authors:

Ren A, Rajashankar KR, Patel DJ

Title:

Fluoride ion encapsulation by Mg2+ ions and phosphates in a fluoride riboswitch.

Journal:

Nature. 2012 May 13;486(7401):85-9. doi: 10.1038/nature11152.

Abstract:

Significant advances in our understanding of RNA architecture, folding and recognition have emerged from structure-function studies on riboswitches, non-coding RNAs whose sensing domains bind small ligands and whose adjacent expression platforms contain RNA elements involved in the control of gene regulation. We now report on the ligand-bound structure of the Thermotoga petrophila fluoride riboswitch, which adopts a higher-order RNA architecture stabilized by pseudoknot and long-range reversed Watson-Crick and Hoogsteen A*U pair formation. The bound fluoride ion is encapsulated within the junctional architecture, anchored in place through direct coordination to three Mg(2+) ions, which in turn are octahedrally coordinated to water molecules and five inwardly pointing backbone phosphates. Our structure of the fluoride riboswitch in the bound state shows how RNA can form a binding pocket selective for fluoride, while discriminating against larger halide ions. The T. petrophila fluoride riboswitch probably functions in gene regulation through a transcription termination mechanism.