title: Conformational changes in the expression domain of the Escherichia coli thiM riboswitch.
abstract: The thiM riboswitch contains an aptamer domain that adaptively binds the coenzyme thiamine pyrophosphate (TPP). The binding of TPP to the aptamer domain induces structural rearrangements that are relayed to a second domain, the so-called expression domain, thereby interfering with gene expression. The recently solved crystal structures of the aptamer domains of the thiM riboswitches in complex with TPP revealed how TPP stabilizes secondary and tertiary structures in the RNA ligand complex. To understand the global modes of reorganization between the two domains upon metabolite binding the structure of the entire riboswitch in presence and absence of TPP needs to be determined. Here we report the secondary structure of the entire thiM riboswitch from Escherichia coli in its TPP-free form and its transition into the TPP-bound variant, thereby depicting domains of the riboswitch that serve as communication links between the aptamer and the expression domain. Furthermore, structural probing provides an explanation for the lack of genetic control exerted by a riboswitch variant with mutations in the expression domain that still binds TPP.
authors.affiliation: LIMES Program Unit Chemical Biology & Medicinal Chemistry, Kekulé Institute for Organic Chemistry & Biochemistry, University of Bonn, Gerhard-Domagk-Strasse 1, D-53121 Bonn, Germany.
authors.forename: Andrea
authors.initials: A
authors.lastname: Rentmeister
authors.forename: Günter
authors.initials: G
authors.lastname: Mayer
authors.forename: Nicole
authors.initials: N
authors.lastname: Kuhn
authors.forename: Michael
authors.initials: M
authors.lastname: Famulok
mesh_terms: D001483:Base Sequence; D004926:Escherichia coli / Q000235:genetics*; D008969:Molecular Sequence Data; D009154:Mutation; D009690:Nucleic Acid Conformation; D012329:RNA, Bacterial / Q000737:chemistry* / Q000378:metabolism; D038621:Regulatory Sequences, Ribonucleic Acid; D013835:Thiamine Pyrophosphate / Q000378:metabolism; D020506:Untranslated Regions / Q000737:chemistry* / Q000378:metabolism
chemical_list: D012329:RNA, Bacterial; D038621:Regulatory Sequences, Ribonucleic Acid; D020506:Untranslated Regions; D013835:Thiamine Pyrophosphate