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rdf:type | |
lifeskim:mentions | |
pubmed:issue |
33
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pubmed:dateCreated |
1997-9-4
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pubmed:abstractText |
To test the hypothesis that the C-terminal half of the Na+/glucose cotransporter (SGLT1) contains the sugar permeation pathway, a cDNA construct (C5) coding for rabbit SGLT1 amino acids 407-662, helices 10-14, was expressed in Xenopus oocytes. Expression and function of C5 was followed by Western blotting, electron microscopy, radioactive tracer, and electrophysiological methods. The C5 protein was synthesized in 20-fold higher levels than SGLT1. The particle density in the protoplasmic face of the oocyte plasma membrane increased 2-fold after C5-cRNA injection compared with noninjected oocytes. The diameters of the C5 particles were heterogeneous (4.8 +/- 0.3, 7.1 +/- 1.2, and 10.3 +/- 0.8 nm) in contrast to the endogenous particles (7.6 +/- 1.2 nm). C5 increased the alpha-methyl-D-glucopyranoside (alphaMDG) uptake up to 20-fold above that of noninjected oocytes and showed an apparent K0.5alphaMDG of 50 mM and a turnover of approximately 660 s-1. Influx was independent of Na+ with transport characteristics similar to those of SGLT1 in the absence of Na+: 1) selective (alphaMDG > D-glucose > D-galactose >> L-glucose approximately D-mannose), 2) inhibited by phloretin, KiPT = approximately 500 microM, and 3) insensitive to phlorizin. These results indicate that C5 behaves as a specific low affinity glucose uniporter. Preliminary studies with three additional constructs, hC5 (the human equivalent of C5), hC4 (human SGLT1 amino acids 407-648, helices 10-13), and hN13 (amino acids 1-648, helices 1-13), further suggest that helices 10-13 form the sugar permeation pathway for SGLT1.
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pubmed:grant | |
pubmed:language |
eng
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pubmed:journal | |
pubmed:citationSubset |
IM
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pubmed:chemical |
http://linkedlifedata.com/resource/pubmed/chemical/Membrane Glycoproteins,
http://linkedlifedata.com/resource/pubmed/chemical/Methylglucosides,
http://linkedlifedata.com/resource/pubmed/chemical/Monosaccharide Transport Proteins,
http://linkedlifedata.com/resource/pubmed/chemical/Peptide Fragments,
http://linkedlifedata.com/resource/pubmed/chemical/Phlorhizin,
http://linkedlifedata.com/resource/pubmed/chemical/Recombinant Proteins,
http://linkedlifedata.com/resource/pubmed/chemical/Sodium-Glucose Transporter 1,
http://linkedlifedata.com/resource/pubmed/chemical/methylglucoside
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pubmed:status |
MEDLINE
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pubmed:month |
Aug
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pubmed:issn |
0021-9258
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pubmed:author | |
pubmed:issnType |
Print
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pubmed:day |
15
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pubmed:volume |
272
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pubmed:owner |
NLM
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pubmed:authorsComplete |
Y
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pubmed:pagination |
20324-7
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pubmed:dateRevised |
2007-11-14
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pubmed:meshHeading |
pubmed-meshheading:9252334-Animals,
pubmed-meshheading:9252334-Carbohydrate Metabolism,
pubmed-meshheading:9252334-Membrane Glycoproteins,
pubmed-meshheading:9252334-Methylglucosides,
pubmed-meshheading:9252334-Monosaccharide Transport Proteins,
pubmed-meshheading:9252334-Peptide Fragments,
pubmed-meshheading:9252334-Phlorhizin,
pubmed-meshheading:9252334-Protein Structure, Secondary,
pubmed-meshheading:9252334-Rabbits,
pubmed-meshheading:9252334-Recombinant Proteins,
pubmed-meshheading:9252334-Sodium-Glucose Transporter 1,
pubmed-meshheading:9252334-Xenopus laevis
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pubmed:year |
1997
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pubmed:articleTitle |
Five transmembrane helices form the sugar pathway through the Na+/glucose cotransporter.
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pubmed:affiliation |
Department of Physiology, UCLA Medical Center, Los Angeles, California 90095-1751, USA. mariana@physiology.medsch.ucla.edu
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pubmed:publicationType |
Journal Article,
Research Support, U.S. Gov't, P.H.S.
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