OEP40, a Regulated Glucose-permeable -Barrel Solute Channel in the Chloroplast Outer Envelope Membrane

Autor(en): Harsman, Anke
Schock, Annette
Hemmis, Birgit
Wahl, Vanessa
Jeshen, Ingrid
Bartsch, Philipp
Schlereth, Armin
Pertl-Obermeyer, Heidi
Goetze, Tom Alexander
Soll, Juergen
Philippar, Katrin
Wagner, Richard 
Stichwörter: ARABIDOPSIS; beta-barrel protein; Biochemistry & Molecular Biology; chloroplast; COLD-ACCLIMATION; DYNAMIC INTERFACE; glucose transport; ion channel; membrane transport; METABOLISM; metabolite transport; outer membrane; PREDICTION; SECONDARY STRUCTURE; solute channel; STARCH DEGRADATION; TRANSCRIPTOME; TRANSPORTERS; TREHALOSE 6-PHOSPHATE
Erscheinungsdatum: 2016
Herausgeber: AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
Journal: JOURNAL OF BIOLOGICAL CHEMISTRY
Volumen: 291
Ausgabe: 34
Startseite: 17848
Seitenende: 17860
Zusammenfassung: 
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 -barrel ion channel with subconductant states in planar lipid bilayers. The OEP40 channel is slightly cation-selective PK+/PCl- approximate to 4:1 and rectifying (i?/i? 2) with a slope conductance of G(max) 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.
DOI: 10.1074/jbc.M115.712398

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