title: Structural insights into the dynamics and function of the C-terminus of the E. coli RNA chaperone Hfq.
abstract: The hexameric Escherichia coli RNA chaperone Hfq (Hfq(Ec)) is involved in riboregulation of target mRNAs by small trans-encoded RNAs. Hfq proteins of different bacteria comprise an evolutionarily conserved core, whereas the C-terminus is variable in length. Although the structure of the conserved core has been elucidated for several Hfq proteins, no structural information has yet been obtained for the C-terminus. Using bioinformatics, nuclear magnetic resonance spectroscopy, synchrotron radiation circular dichroism (SRCD) spectroscopy and small angle X-ray scattering we provide for the first time insights into the conformation and dynamic properties of the C-terminal extension of Hfq(Ec). These studies indicate that the C-termini are flexible and extend laterally away from the hexameric core, displaying in this way features typical of intrinsically disordered proteins that facilitate intermolecular interactions. We identified a minimal, intrinsically disordered region of the C-terminus supporting the interactions with longer RNA fragments. This minimal region together with rest of the C-terminal extension provides a flexible moiety capable of tethering long and structurally diverse RNA molecules. Furthermore, SRCD spectroscopy supported the hypothesis that RNA fragments exceeding a certain length interact with the C-termini of Hfq(Ec).
authors.affiliation: Department of Structural and Computational Biology, Max F. Perutz Laboratories, University of Vienna, Campus Vienna Biocenter 5, A-1030 Vienna, Austria.
authors.forename: Mads
authors.initials: M
authors.lastname: Beich-Frandsen
authors.forename: Branislav
authors.initials: B
authors.lastname: Vecerek
authors.forename: Petr V
authors.initials: PV
authors.lastname: Konarev
authors.forename: Björn
authors.initials: B
authors.lastname: Sjöblom
authors.forename: Karin
authors.initials: K
authors.lastname: Kloiber
authors.forename: Hermann
authors.initials: H
authors.lastname: Hämmerle
authors.forename: Lukas
authors.initials: L
authors.lastname: Rajkowitsch
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Miles
authors.forename: Georg
authors.initials: G
authors.lastname: Kontaxis
authors.forename: B A
authors.initials: BA
authors.lastname: Wallace
authors.forename: Dimitri I
authors.initials: DI
authors.lastname: Svergun
authors.forename: Robert
authors.initials: R
authors.lastname: Konrat
authors.forename: Udo
authors.initials: U
authors.lastname: Bläsi
authors.forename: Kristina
authors.initials: K
authors.lastname: Djinovic-Carugo
mesh_terms: D002942:Circular Dichroism; D019295:Computational Biology; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000235:genetics; D035001:Host Factor 1 Protein / Q000737:chemistry* / Q000235:genetics; D008958:Models, Molecular; D019906:Nuclear Magnetic Resonance, Biomolecular; D011487:Protein Conformation; D012313:RNA / Q000737:chemistry; D017384:Sequence Deletion
chemical_list: D029968:Escherichia coli Proteins; C087373:Hfq protein, E coli; D035001:Host Factor 1 Protein; D012313:RNA