![]()
|
|
||||||||
J. Biol. Chem., Vol. 275, Issue 34, 25959-25964, August 25, 2000
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
From the Department of Physiology, UCLA School of Medicine,
Los Angeles, California 90095-1751
The Vibrio
parahaemolyticus sodium/glucose
transporter (vSGLT) is a bacterial member of the SGLT gene
family. Wild-type and mutant vSGLT proteins were expressed in
Escherichia coli, and transport activity was measured in
intact cells and plasma membrane vesicles. Two cysteine-less vSGLT
proteins exhibited sugar transport rates comparable with that of the
wild-type protein. Six residues in two regions of vSGLT known to be of
functional importance in SGLT1 were replaced individually with cysteine
in the cysteine-less protein. Characterization of these single
cysteine-substituted vSGLTs showed that two residues (Gly-151 and
Gln-428) are essential for transport function, whereas the other four
residues (Leu-147, Leu-149, Ala-423, and Gln-425) are not.
2-Aminoethylmethanethiosulfonate (MTSEA) blocked
Na+/glucose transport by only the transporter bearing a
cysteine at position 425 (Q425C). MTSEA inhibition was reversed by
dithiothreitol and blocked by the presence of both Na+ and
D-glucose, indicating that conformational changes of the vSGLT protein are involved in Na+/glucose transport. A
split version of vSGLT was generated by co-expression of the N-terminal
(N7) and C-terminal (C7) halves of the
transporter. The split vSGLT maintained
Na+-dependent glucose transport activity.
Chemical cross-linking of split vSGLT, with a cysteine in each
N7 and C7 fragment, suggested that hydrophilic
loops between helices 4 and 5 and between helices 10 and 11 are within
8 Å of each other. We conclude that the mechanism of
Na+/glucose transport by vSGLT is similar to mammalian
SGLTs and that further studies on vSGLT will provide novel insight to
the structure and function of this class of cotransporters.
Characterization of the Vibrio
parahaemolyticus Na+/Glucose Cotransporter
A BACTERIAL MEMBER OF THE SODIUM/GLUCOSE TRANSPORTER (SGLT)
FAMILY*
*
Support was provided by United States Public Health Service
Grants DK 19567 and DK 44602.The costs of publication of this article were defrayed in part by the
payment of page charges. The article
must therefore be hereby marked
"advertisement" in accordance with 18 U.S.C. Section
1734 solely to indicate this fact.
To whom correspondence should be addressed. Tel.: 310-825-6905;
Fax: 310-206-5886; E-mail: ewright@mednet.ucla.edu.
This article has been cited by other articles:
![]() |
G. Jeschke, C. Wegener, M. Nietschke, H. Jung, and H.-J. Steinhoff Interresidual Distance Determination by Four-Pulse Double Electron-Electron Resonance in an Integral Membrane Protein: The Na+/Proline Transporter PutP of Escherichia coli Biophys. J., April 1, 2004; 86(4): 2551 - 2557. [Abstract] [Full Text] [PDF] |
||||
![]() |
E. M. Wright Renal Na+-glucose cotransporters Am J Physiol Renal Physiol, January 1, 2001; 280(1): F10 - F18. [Abstract] [Full Text] [PDF] |
||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| All ASBMB Journals | Molecular and Cellular Proteomics |
| Journal of Lipid Research | ASBMB Today |