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Publication Abstract from PubMed

Riboswitches are structural elements found in mRNA molecules that couple small-molecule binding to regulation of gene expression, usually by controlling transcription or translation. We have determined high-resolution crystal structures of the ykkC guanidine III riboswitch from Thermobifida fusca. The riboswitch forms a classic H-type pseudoknot that includes a triple helix that is continuous with a central core of conserved nucleotides. These form a left-handed helical ramp of inter-nucleotide interactions, generating the guanidinium cation binding site. The ligand is hydrogen bonded to the Hoogsteen edges of two guanine bases. The binding pocket has a side opening that can accommodate a small side chain, shown by structures with bound methylguanidine, aminoguanidine, ethylguanidine, and agmatine. Comparison of the new structure with those of the guanidine I and II riboswitches reveals that evolution generated three different structural solutions for guanidine binding and subsequent gene regulation, although with some common elements.

Structure of the Guanidine III Riboswitch.,Huang L, Wang J, Wilson TJ, Lilley DMJ Cell Chem Biol. 2017 Sep 28. pii: S2451-9456(17)30319-7. doi:, 10.1016/j.chembiol.2017.08.021. PMID:28988949^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.