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Detection of Detergent-sensitive Interactions Between Membrane Proteins
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Five transmembrane helices form the sugar pathway through the Na+/glucose cotransporter
M Panayotova-Heiermann1, S Eskandari, E Turk
1Department of Physiology, UCLA Medical Center, Los Angeles, California 90095-1751, USA. mariana@physiology.medsch.ucla.edu
The Journal of Biological Chemistry
|August 15, 1997
Summary
The C-terminal half of the Na+/glucose cotransporter (SGLT1) forms a sugar permeation pathway. This region, when expressed, functions as a glucose uniporter, independent of sodium.
Area of Science:
- Biochemistry
- Molecular Biology
- Membrane Transport
Background:
- The Na+/glucose cotransporter (SGLT1) is crucial for glucose absorption.
- Identifying the specific regions responsible for sugar transport is essential for understanding its mechanism.
Purpose of the Study:
- To investigate whether the C-terminal half of SGLT1 contains the sugar permeation pathway.
- To characterize the functional properties of this proposed pathway.
Main Methods:
- Expression of a rabbit SGLT1 C-terminal construct (C5) in Xenopus oocytes.
- Analysis using Western blotting, electron microscopy, radioactive tracer uptake, and electrophysiology.
- Functional assays with various glucose analogs and inhibitors.
Main Results:
- The C5 construct was highly expressed and formed distinct particles in the oocyte membrane.
- C5 mediated Na+-independent glucose uptake with characteristics similar to SGLT1.
- The transport was selective for glucose and inhibited by phloretin, confirming it acts as a glucose uniporter.
Conclusions:
- The C-terminal half of SGLT1, specifically helices 10-13, likely forms the sugar permeation pathway.
- This region functions as a low-affinity glucose uniporter.
- Further studies with human constructs support these findings.
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