title: OEP40, a Regulated Glucose-permeable β-Barrel Solute Channel in the Chloroplast Outer Envelope Membrane.
abstract: Chloroplasts and mitochondria are unique endosymbiotic cellular organelles surrounded by two membranes. Essential metabolic networking between these compartments and their hosting cells requires the exchange of a large number of biochemical pathway intermediates in a directed and coordinated fashion across their inner and outer envelope membranes. Here, we describe the identification and functional characterization of a highly specific, regulated solute channel in the outer envelope of chloroplasts, named OEP40. Loss of OEP40 function in Arabidopsis thaliana results in early flowering under cold temperature. The reconstituted recombinant OEP40 protein forms a high conductance β-barrel ion channel with subconductant states in planar lipid bilayers. The OEP40 channel is slightly cation-selective PK+/PCl- ≈ 4:1 and rectifying (i⃗/i⃖ ≅ 2) with a slope conductance of Ḡmax ≅ 690 picosiemens. The OEP40 channel has a restriction zone diameter of ≅1.4 nm and is permeable for glucose, glucose 1-phosphate and glucose 6-phosphate, but not for maltose. Moreover, channel properties are regulated by trehalose 6-phosphate, which cannot permeate. Altogether, our results indicate that OEP40 is a "glucose-gate" in the outer envelope membrane of chloroplasts, facilitating selective metabolite exchange between chloroplasts and the surrounding cell.
authors.affiliation: From the Institute of Biophysics, Department of Biology, University of Osnabrück, Barbarastrasse 13, 49076 Osnabrück.
authors.forename: Anke
authors.initials: A
authors.lastname: Harsman
authors.affiliation: the Chair of Plant Biochemistry and Physiology, Department Biology I-Botany, Ludwig-Maximilians-University München, Grosshadernerstrasse 2-4, D-82152 Planegg-Martinsried, the Munich Centre for Integrated Protein Science, Ludwig-Maximilians-University München, D-81377 München, and.
authors.forename: Annette
authors.initials: A
authors.lastname: Schock
authors.affiliation: From the Institute of Biophysics, Department of Biology, University of Osnabrück, Barbarastrasse 13, 49076 Osnabrück.
authors.forename: Birgit
authors.initials: B
authors.lastname: Hemmis
authors.affiliation: the Department of Metabolic Networks, Max Planck Institute of Molecular Plant Physiology, Am Mühlenberg 1, 14476 Potsdam, Germany.
authors.forename: Vanessa
authors.initials: V
authors.lastname: Wahl
authors.affiliation: the Chair of Plant Biochemistry and Physiology, Department Biology I-Botany, Ludwig-Maximilians-University München, Grosshadernerstrasse 2-4, D-82152 Planegg-Martinsried, the Munich Centre for Integrated Protein Science, Ludwig-Maximilians-University München, D-81377 München, and.
authors.forename: Ingrid
authors.initials: I
authors.lastname: Jeshen
authors.affiliation: From the Institute of Biophysics, Department of Biology, University of Osnabrück, Barbarastrasse 13, 49076 Osnabrück.
authors.forename: Philipp
authors.initials: P
authors.lastname: Bartsch
authors.affiliation: the Department of Metabolic Networks, Max Planck Institute of Molecular Plant Physiology, Am Mühlenberg 1, 14476 Potsdam, Germany.
authors.forename: Armin
authors.initials: A
authors.lastname: Schlereth
authors.affiliation: the Chair of Plant Biochemistry and Physiology, Department Biology I-Botany, Ludwig-Maximilians-University München, Grosshadernerstrasse 2-4, D-82152 Planegg-Martinsried, the Munich Centre for Integrated Protein Science, Ludwig-Maximilians-University München, D-81377 München, and.
authors.forename: Heidi
authors.initials: H
authors.lastname: Pertl-Obermeyer
authors.affiliation: the Chair of Plant Biochemistry and Physiology, Department Biology I-Botany, Ludwig-Maximilians-University München, Grosshadernerstrasse 2-4, D-82152 Planegg-Martinsried, the Munich Centre for Integrated Protein Science, Ludwig-Maximilians-University München, D-81377 München, and.
authors.forename: Tom Alexander
authors.initials: TA
authors.lastname: Goetze
authors.affiliation: the Chair of Plant Biochemistry and Physiology, Department Biology I-Botany, Ludwig-Maximilians-University München, Grosshadernerstrasse 2-4, D-82152 Planegg-Martinsried, the Munich Centre for Integrated Protein Science, Ludwig-Maximilians-University München, D-81377 München, and.
authors.forename: Jürgen
authors.initials: J
authors.lastname: Soll
authors.affiliation: the Chair of Plant Biochemistry and Physiology, Department Biology I-Botany, Ludwig-Maximilians-University München, Grosshadernerstrasse 2-4, D-82152 Planegg-Martinsried, the Munich Centre for Integrated Protein Science, Ludwig-Maximilians-University München, D-81377 München, and philippar@lmu.de.
authors.forename: Katrin
authors.initials: K
authors.lastname: Philippar
authors.affiliation: From the Institute of Biophysics, Department of Biology, University of Osnabrück, Barbarastrasse 13, 49076 Osnabrück, ri.wagner@jacobs-university.de.
authors.forename: Richard
authors.initials: R
authors.lastname: Wagner
mesh_terms: D017360:Arabidopsis / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D060365:Chloroplast Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D002736:Chloroplasts / Q000737:chemistry* / Q000378:metabolism; D005947:Glucose / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D007425:Intracellular Membranes / Q000737:chemistry* / Q000378:metabolism; D008051:Lipid Bilayers / Q000737:chemistry / Q000378:metabolism; D008565:Membrane Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D060365:Chloroplast Proteins; D008051:Lipid Bilayers; D008565:Membrane Proteins; D005947:Glucose
keywords: beta-barrel protein; chloroplast; glucose transport; ion channel; membrane transport; metabolite transport; outer membrane; solute channel