Amyloplasts were isolated and purified from wheat endosperm and the envelope membranes reconstituted into liposomes. Envelope membranes were solubilized in n-octyl β-D-glucopyranoside and mixed with liposomes supplemented with 5.6 mol% cholesterol to produce proteoliposomes of defined size, which showed negligible leakage of internal substrates. Transport experiments with proteoliposomes revealed a counter-exchange of glucose 1-phosphate (Glc1P), glucose 6-phosphate (Glc6P), inorganic phosphate (Pi), 3-phosphoglycerate and dihydroxyacetone phosphate. The Glc1P/Pi counter-exchange reaction exhibited an apparent Km for Glc1P of 0.4 mM. Glc6P was a competitive inhibitor of Glc1P transport (Ki 0.8 mM), and the two hexose phosphates could exchange with each other, indicating the operation of a single carrier protein. Glc1P/Pi antiport in proteoliposomes showed an exchange stoichiometry at pH 8.0 of 1 mol of phosphate transported per mol of sugar phosphate.
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November 1996
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Research Article|
November 01 1996
Reconstitution of the hexose phosphate translocator from the envelope membranes of wheat endosperm amyloplasts
Ian J TETLOW;
Ian J TETLOW
*
1School of Biological Sciences, 3.614 Stopford Building, University of Manchester, Manchester M13 9PT, U.K.
*To whom correspondence should be addressed.
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Caroline G BOWSHER;
Caroline G BOWSHER
1School of Biological Sciences, 3.614 Stopford Building, University of Manchester, Manchester M13 9PT, U.K.
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Michael J EMES
Michael J EMES
1School of Biological Sciences, 3.614 Stopford Building, University of Manchester, Manchester M13 9PT, U.K.
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Publisher: Portland Press Ltd
Received:
May 17 1996
Revision Received:
July 09 1996
Accepted:
July 12 1996
Online ISSN: 1470-8728
Print ISSN: 0264-6021
The Biochemical Society, London © 1996
1996
Biochem J (1996) 319 (3): 717–723.
Article history
Received:
May 17 1996
Revision Received:
July 09 1996
Accepted:
July 12 1996
Citation
Ian J TETLOW, Caroline G BOWSHER, Michael J EMES; Reconstitution of the hexose phosphate translocator from the envelope membranes of wheat endosperm amyloplasts. Biochem J 1 November 1996; 319 (3): 717–723. doi: https://doi.org/10.1042/bj3190717
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