title: Structural insight into the role of the Ton complex in energy transduction.
abstract: In Gram-negative bacteria, outer membrane transporters import nutrients by coupling to an inner membrane protein complex called the Ton complex. The Ton complex consists of TonB, ExbB, and ExbD, and uses the proton motive force at the inner membrane to transduce energy to the outer membrane via TonB. Here, we structurally characterize the Ton complex from Escherichia coli using X-ray crystallography, electron microscopy, double electron-electron resonance (DEER) spectroscopy, and crosslinking. Our results reveal a stoichiometry consisting of a pentamer of ExbB, a dimer of ExbD, and at least one TonB. Electrophysiology studies show that the Ton subcomplex forms pH-sensitive cation-selective channels and provide insight into the mechanism by which it may harness the proton motive force to produce energy.
authors.affiliation: Laboratoire d'Ingénierie des Systèmes Macromoléculaires, UMR7255 CNRS/Aix-Marseille Université, Institut de Microbiologie de la Méditerranée, 13402 Marseille Cedex 20, France.|National Institute of Diabetes &Digestive &Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA.
authors.forename: Hervé
authors.initials: H
authors.lastname: Celia
authors.affiliation: Markey Center for Structural Biology, Department of Biological Sciences, and the Purdue Institute for Inflammation, Immunology and Infectious Diseases, Purdue University, West Lafayette, Indiana 47907, USA.
authors.forename: Nicholas
authors.initials: N
authors.lastname: Noinaj
authors.affiliation: Markey Center for Structural Biology, Department of Biological Sciences, and the Purdue Institute for Inflammation, Immunology and Infectious Diseases, Purdue University, West Lafayette, Indiana 47907, USA.
authors.forename: Stanislav D
authors.initials: SD
authors.lastname: Zakharov
authors.affiliation: Fachbereich Physik, Freie Universität, 14195 Berlin, Germany.|Faculty of Chemistry and Biochemistry, Ruhr-Universität Bochum, 45810 Bochum, Germany.
authors.forename: Enrica
authors.initials: E
authors.lastname: Bordignon
authors.affiliation: National Institute of Diabetes &Digestive &Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA.
authors.forename: Istvan
authors.initials: I
authors.lastname: Botos
authors.affiliation: Departamento de Cirugia Experimental, Instituto de Investigacion Hospital La Paz (IdiPAZ), Paseo de la Castellana 261, 28046 Madrid, Spain.
authors.forename: Monica
authors.initials: M
authors.lastname: Santamaria
authors.affiliation: National Institute of Diabetes &Digestive &Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA.
authors.forename: Travis J
authors.initials: TJ
authors.lastname: Barnard
authors.affiliation: Markey Center for Structural Biology, Department of Biological Sciences, and the Purdue Institute for Inflammation, Immunology and Infectious Diseases, Purdue University, West Lafayette, Indiana 47907, USA.
authors.forename: William A
authors.initials: WA
authors.lastname: Cramer
authors.affiliation: Laboratoire d'Ingénierie des Systèmes Macromoléculaires, UMR7255 CNRS/Aix-Marseille Université, Institut de Microbiologie de la Méditerranée, 13402 Marseille Cedex 20, France.
authors.forename: Roland
authors.initials: R
authors.lastname: Lloubes
authors.affiliation: National Institute of Diabetes &Digestive &Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA.
authors.forename: Susan K
authors.initials: SK
authors.lastname: Buchanan
mesh_terms: D018360:Crystallography, X-Ray; D004926:Escherichia coli / Q000737:chemistry* / Q000648:ultrastructure; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000378:metabolism* / Q000648:ultrastructure; D006863:Hydrogen-Ion Concentration; D008565:Membrane Proteins / Q000737:chemistry* / Q000378:metabolism* / Q000648:ultrastructure; D046912:Multiprotein Complexes / Q000737:chemistry* / Q000378:metabolism* / Q000648:ultrastructure; D018892:Proton-Motive Force
chemical_list: D029968:Escherichia coli Proteins; C052874:ExbB protein, E coli; D008565:Membrane Proteins; D046912:Multiprotein Complexes; C489181:tonB protein, E coli; C060790:exbD protein, E coli