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J. Biol. Chem., Vol. 281, Issue 17, 12020-12029, April 28, 2006

This Article Full Text Full Text (PDF) Supplemental Data All Versions of this Article: 281/17/12020    most recent M513586200v1 Submit a Letter to Editor Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Hemmler, R. Articles by Wagner, R. Search for Related Content PubMed PubMed Citation Articles by Hemmler, R. Articles by Wagner, R. Social Bookmarking                      What's this?

Molecular Properties of Oep21, an ATP-regulated Anion-selective Solute Channel from the Outer Chloroplast Membrane^*

Roland Hemmler¹, Thomas Becker, Enrico Schleiff, Bettina Bölter, Tanja Stahl, Jürgen Soll, Tom A. Götze, Simona Braams, and Richard Wagner²

From the Biophysik, Universität Osnabrück, FB Biologie/Chemie, Barbarastrasse 11, D-49034 Osnabrück, Germany and the Department of Biology I, LMU München, Menzinger Strasse 67, 80638 München, Germany

The flux of phosphorylated carbohydrates, the major export products of chloroplasts, is regulated at the level of the inner and presumably also at the level of the outer membrane. This is achieved through modulation of the outer membrane Oep21 channel currents and tuning of its ion selectivity. Refined analysis of the Oep21 channel properties by biochemical and electrophysiological methods revealed a channel formed by eight -strands with a wider pore vestibule of d_vest 2.4 nm at the intermembrane site and a narrower filter pore of d_restr 1 nm. The Oep21 pore contains two high affinity sites for ATP, one located at a relative transmembrane electrical distance = 0.56 and the second close to the vestibule at the intermembrane site. The ATP-dependent current block and reduction in anion selectivity of the Oep21 channel is relieved by the competitive binding of phosphorylated metabolic intermediates like 3-phosphoglycerate and glycerinaldehyde 3-phosphate. Deletion of a C-terminal putative FX₄K binding motif in Oep21 decreased the capability of the channel to tune its ion selectivity by about 50%, whereas current block remained unchanged.

Received for publication, December 21, 2005 , and in revised form, February 9, 2006.

^* This work was supported by Deutsche Forschungsgemeinschaft Grants SPP1108 (to R. W. and J. S.) and SFBTR01 (to E. S.). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

The on-line version of this article (available at http://www.jbc.org) contains supplemental Fig. 1S.

¹ Present address: Ionovation GmbH, 49084 Osnabrück, Germany.

² To whom correspondence should be addressed. Tel.: 49-541-969-2851; Fax: 49-541-969-2243; E-mail: wagner{at}uos.de.

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				T. A. Goetze, K. Philippar, I. Ilkavets, J. Soll, and R. Wagner OEP37 Is a New Member of the Chloroplast Outer Membrane Ion Channels J. Biol. Chem., June 30, 2006; 281(26): 17989 - 17998. [Abstract] [Full Text] [PDF]