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Single-molecule FRET reveals the energy landscape of the full-length SAM-I riboswitch

Manz, Christoph 1,2; Kobitski, Andrei Yu 1; Samanta, Ayan; Keller, Bettina G.; Jäschke, Andres 2; Nienhaus, G. Ulrich ORCID iD icon 1,2,3,4
1 Institut für Angewandte Physik (APH), Karlsruher Institut für Technologie (KIT)
2 Heidelberg Karlsruhe Research Partnership (HEiKA), Karlsruher Institut für Technologie (KIT)
3 Institut für Toxikologie und Genetik (ITG), Karlsruher Institut für Technologie (KIT)
4 Institut für Nanotechnologie (INT), Karlsruher Institut für Technologie (KIT)

Abstract (englisch):

S-adenosyl-L-methionine (SAM) ligand binding induces major structural changes in SAM-I riboswitches, through which gene expression is regulated via transcription termination. Little is known about the conformations and motions governing the function of the full-length Bacillus subtilis yitJ SAM-I riboswitch. Therefore, we have explored its conformational energy landscape as a function of Mg2+ and SAM ligand concentrations using single-molecule Förster resonance energy transfer (smFRET) microscopy and hidden Markov modeling analysis. We resolved four conformational states both in the presence and the absence of SAM and determined their Mg2+-dependent fractional populations and conformational dynamics, including state lifetimes, interconversion rate coefficients and equilibration timescales. Riboswitches with terminator and antiterminator folds coexist, and SAM binding only gradually shifts the populations toward terminator states. We observed a pronounced acceleration of conformational transitions upon SAM binding, which may be crucial for off-switching during the brief decision window before expression of the downstream gene.

DOI: 10.1038/nchembio.2476
Zitationen: 39
Zitationen: 47
Zugehörige Institution(en) am KIT Institut für Angewandte Physik (APH)
Institut für Nanotechnologie (INT)
Institut für Toxikologie und Genetik (ITG)
Universität Karlsruhe (TH) – Interfakultative Einrichtungen (Interfakultative Einrichtungen)
Karlsruhe School of Optics & Photonics (KSOP)
Publikationstyp Zeitschriftenaufsatz
Publikationsdatum 18.09.2017
Sprache Englisch
Identifikator ISSN: 1552-4450, 1552-4469
KITopen-ID: 1000076142
HGF-Programm 43.23.01 (POF III, LK 01) Advanced Optical Lithography+Microscopy
Erschienen in Nature chemical biology
Verlag Nature Research
Band 13
Heft 11
Seiten 1172–1178
Nachgewiesen in Dimensions
Web of Science
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