title: Neutrons describe ectoine effects on water H-bonding and hydration around a soluble protein and a cell membrane.
abstract: Understanding adaptation to extreme environments remains a challenge of high biotechnological potential for fundamental molecular biology. The cytosol of many microorganisms, isolated from saline environments, reversibly accumulates molar concentrations of the osmolyte ectoine to counterbalance fluctuating external salt concentrations. Although they have been studied extensively by thermodynamic and spectroscopic methods, direct experimental structural data have, so far, been lacking on ectoine-water-protein interactions. In this paper, in vivo deuterium labeling, small angle neutron scattering, neutron membrane diffraction and inelastic scattering are combined with neutron liquids diffraction to characterize the extreme ectoine-containing solvent and its effects on purple membrane of H. salinarum and E. coli maltose binding protein. The data reveal that ectoine is excluded from the hydration layer at the membrane surface and does not affect membrane molecular dynamics, and prove a previous hypothesis that ectoine is excluded from a monolayer of dense hydration water around the soluble protein. Neutron liquids diffraction to atomic resolution shows how ectoine enhances the remarkable properties of H-bonds in water-properties that are essential for the proper organization, stabilization and dynamics of biological structures.
authors.affiliation: Institut Laue Langevin, F-38042 Grenoble, France.|CNRS, IBS, F-38044 Grenoble, France.|CEA, IBS, F-38044 Grenoble, France.|Univ. Grenoble Alpes, IBS, F-38044 Grenoble, France.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Zaccai
authors.affiliation: Bitop, Stockumer Str. 28, 58453 Witten, Germany.
authors.forename: Irina
authors.initials: I
authors.lastname: Bagyan
authors.affiliation: Institut Laue Langevin, F-38042 Grenoble, France.|Institut Charles Sadron CNRS-UdS, 23 rue du Loess, BP 84047, 67034 Strasbourg Cedex 2, France.
authors.forename: Jérôme
authors.initials: J
authors.lastname: Combet
authors.affiliation: Institut Laue Langevin, F-38042 Grenoble, France.
authors.forename: Gabriel J
authors.initials: GJ
authors.lastname: Cuello
authors.affiliation: Institut Laue Langevin, F-38042 Grenoble, France.
authors.forename: Bruno
authors.initials: B
authors.lastname: Demé
authors.affiliation: CNRS, IBS, F-38044 Grenoble, France.|CEA, IBS, F-38044 Grenoble, France.|Univ. Grenoble Alpes, IBS, F-38044 Grenoble, France.
authors.forename: Yann
authors.initials: Y
authors.lastname: Fichou
authors.affiliation: CNRS, IBS, F-38044 Grenoble, France.|CEA, IBS, F-38044 Grenoble, France.|Univ. Grenoble Alpes, IBS, F-38044 Grenoble, France.
authors.forename: François-Xavier
authors.initials: FX
authors.lastname: Gallat
authors.affiliation: Institut Laue Langevin, F-38042 Grenoble, France.
authors.forename: Victor M
authors.initials: VM
authors.lastname: Galvan Josa
authors.affiliation: Max-Planck-Institute of Biochemistry, Department of Membrane Biochemistry, Martinsried, Germany.
authors.forename: Susanne
authors.initials: S
authors.lastname: von Gronau
authors.affiliation: Institut Laue Langevin, F-38042 Grenoble, France.
authors.forename: Michael
authors.initials: M
authors.lastname: Haertlein
authors.affiliation: Institut Laue Langevin, F-38042 Grenoble, France.
authors.forename: Anne
authors.initials: A
authors.lastname: Martel
authors.affiliation: Institut Laue Langevin, F-38042 Grenoble, France.
authors.forename: Martine
authors.initials: M
authors.lastname: Moulin
authors.affiliation: Bitop, Stockumer Str. 28, 58453 Witten, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Neumann
authors.affiliation: CNRS, IBS, F-38044 Grenoble, France.|CEA, IBS, F-38044 Grenoble, France.|Univ. Grenoble Alpes, IBS, F-38044 Grenoble, France.
authors.forename: Martin
authors.initials: M
authors.lastname: Weik
authors.affiliation: Max-Planck-Institute of Biochemistry, Department of Membrane Biochemistry, Martinsried, Germany.
authors.forename: Dieter
authors.initials: D
authors.lastname: Oesterhelt
mesh_terms: D000599:Amino Acids, Diamino / Q000378:metabolism*; D001426:Bacterial Proteins / Q000378:metabolism; D002462:Cell Membrane / Q000737:chemistry*; D003903:Deuterium / Q000378:metabolism; D004926:Escherichia coli / Q000737:chemistry*; D020632:Halomonas / Q000737:chemistry*; D006860:Hydrogen Bonding; D007553:Isotope Labeling; D033363:Neutron Diffraction; D053838:Scattering, Small Angle; D014867:Water / Q000032:analysis*
chemical_list: D000599:Amino Acids, Diamino; D001426:Bacterial Proteins; D014867:Water; C045628:ectoine; D003903:Deuterium