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B. Hirayama, M. Lostao, M. Panayotova-Heiermann, D. Loo, E. Turk, Ernest Wright (1996)
Kinetic and specificity differences between rat, human, and rabbit Na+-glucose cotransporters (SGLT-1).The American journal of physiology, 270 6 Pt 1
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Relaxation kinetics of the Na+/glucose cotransporter.Proceedings of the National Academy of Sciences of the United States of America, 90 12
D. Loo, B. Hirayama, E. Gallardo, Jason Lam, E. Turk, Ernest Wright (1998)
Conformational changes couple Na+ and glucose transport.Proceedings of the National Academy of Sciences of the United States of America, 95 13
M. Lostao, B. Hirayama, D. Loo, E. Wright (1994)
Phenylglucosides and the Na+/glucose cotransporter (SGLT1): Analysis of interactionsThe Journal of Membrane Biology, 142
A Hazama, DDF Loo, EM Wright (1997)
Pre-steady-state currents of the Na+/glucose cotransporter (SGLT1)J Membr Biol, 155
Shauna Loewen, S. Yao, Melissa Slugoski, Nadira Mohabir, R. Turner, J. Mackey, J. Weiner, M. Gallagher, P. Henderson, S. Baldwin, C. Cass, J. Young (2004)
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S. Eskandari, E. Wright, D. Loo (2005)
Kinetics of the Reverse Mode of the Na+/Glucose CotransporterThe Journal of Membrane Biology, 204
B. Hirayama, D. Loo, A. Diez-Sampedro, D. Leung, A. Meinild, Mary Lai-Bing, E. Turk, E. Wright (2007)
Sodium-dependent reorganization of the sugar-binding site of SGLT1.Biochemistry, 46 46
E. Briasoulis, I. Judson, N. Pavlidis, P. Beale, J. Wanders, Y. Groot, Gijbert Veerman, Martina Schuessler, G. Niebch, K. Siamopoulos, E. Tzamakou, D. Rammou, L. Wolf, R. Walker, A. Hanauske (2000)
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D. Loo, B. Hirayama, M. Karakossian, A. Meinild, E. Wright (2006)
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A. Diez-Sampedro, E. Wright, B. Hirayama (2001)
Residue 457 Controls Sugar Binding and Transport in the Na+/Glucose Cotransporter*The Journal of Biological Chemistry, 276
D. Loo, S. Eskandari, B. Hirayama, E. Wright (2002)
A Kinetic Model for Secondary Active Transport
B. Hirayama, A. Diez-Sampedro, E. Wright (2001)
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Nucleoside transporters: from scavengers to novel therapeutic targets.Trends in pharmacological sciences, 27 8
D. Loo, B. Hirayama, A. Cha, F. Bezanilla, E. Wright (2005)
Perturbation Analysis of the Voltage-sensitive Conformational Changes of the Na+/Glucose CotransporterThe Journal of General Physiology, 125
A. Meinild, B. Hirayama, E. Wright, D. Loo (2002)
Fluorescence studies of ligand-induced conformational changes of the Na(+)/glucose cotransporter.Biochemistry, 41 4
I. Knütter, B. Hartrodt, G. Tóth, A. Keresztes, G. Kottra, C. Mrestani‐Klaus, I. Born, H. Daniel, K. Neubert, M. Brandsch (2007)
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Electrophysiological characterization of a recombinant human Na+‐coupled nucleoside transporter (hCNT1) produced in Xenopus oocytesThe Journal of Physiology, 558
D. Loo, B. Hirayama, A. Meinild, G. Chandy, T. Zeuthen, E. Wright (1999)
Passive water and ion transport by cotransportersThe Journal of Physiology, 518
M. Sala-Rabanal, D. Loo, B. Hirayama, E. Wright (2008)
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B. Birnir, D. Loo, E. Wright (1991)
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A. Diez-Sampedro, M. Lostao, E. Wright, B. Hirayama (2000)
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Said Falk, Alexandre Guay, C. Chenu, Shivakumar Patil, A. Berteloot (1998)
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B. Mackenzie, D. Loo, E. Wright (1998)
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A. Hazama, D. Loo, E. Wright (1997)
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I. Larráyoz, F. Casado, M. Pastor-Anglada, M. Lostao (2004)
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J. Mackey, S. Yao, Kyla Smith, E. Karpinski, S. Baldwin, C. Cass, J. Young (1999)
Gemcitabine transport in xenopus oocytes expressing recombinant plasma membrane mammalian nucleoside transporters.Journal of the National Cancer Institute, 91 21
B. Hirayama, D. Loo, E. Wright (1997)
Cation Effects on Protein Conformation and Transport in the Na+/Glucose Cotransporter*The Journal of Biological Chemistry, 272
G. Zampighi, M. Kreman, K. Boorer, D. Loo, F. Bezanilla, G. Chandy, James Hall, E. Wright (1995)
A method for determining the unitary functional capacity of cloned channels and transporters expressed in Xenopus laevis oocytesThe Journal of Membrane Biology, 148
M. Veenstra, S. Lanza, B. Hirayama, E. Turk, E. Wright (2004)
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L. Parent, S. Supplisson, D. Loo, E. Wright (2004)
Electrogenic properties of the cloned Na+/glucose cotransporter: II. A transport model under nonrapid equilibrium conditionsThe Journal of Membrane Biology, 125
M. Sala-Rabanal, D. Loo, B. Hirayama, E. Turk, E. Wright (2006)
Molecular interactions between dipeptides, drugs and the human intestinal H+–oligopeptide cotransporter hPEPT1The Journal of Physiology, 574
S. Yao, A. Ng, M. Ritzel, W. Gati, C. Cass, J. Young (1996)
Transport of adenosine by recombinant purine- and pyrimidine-selective sodium/nucleoside cotransporters from rat jejunum expressed in Xenopus laevis oocytes.Molecular pharmacology, 50 6
BA Hirayama, DDF Loo, A Díez-Sampedro, DW Leung, A-K Meinild, M Lai-Bing, E Turk, EM Wright (2007)
Na-dependent reorganization of the sugar-binding site of SGLT1Biochemistry, 46
M. Quick, D. Loo, E. Wright (2001)
Neutralization of a Conserved Amino Acid Residue in the Human Na+/Glucose Transporter (hSGLT1) Generates a Glucose-gated H+ Channel*The Journal of Biological Chemistry, 276
Drugs are transported by cotransporters with widely different turnover rates. We have examined the underlying mechanism using, as a model system, glucose and indican (indoxyl-β-d-glucopyranoside) transport by human Na+/glucose cotransporter (hSGLT1). Indican is transported by hSGLT1 at 10% of the rate for glucose but with a fivefold higher apparent affinity. We expressed wild-type hSGLT1 and mutant G507C in Xenopus oocytes and used electrical and optical methods to measure the kinetics of glucose (using nonmetabolized glucose analogue α-methyl-d-glucopyranoside, αMDG) and indican transport, alone and together. Indican behaved as a competitive inhibitor of αMDG transport. To examine protein conformations, we recorded SGLT1 capacitive currents (charge movements) and fluorescence changes in response to step jumps in membrane voltage, in the presence and absence of indican and/or αMDG. In the absence of sugar, voltage jumps elicited capacitive SGLT currents that decayed to steady state with time constants (τ) of 3–20 ms. These transient currents were abolished in saturating αMDG but only slightly reduced (10%) in saturating indican. SGLT1 G507C rhodamine fluorescence intensity increased with depolarizing and decreased with hyperpolarizing voltages. Maximal fluorescence increased ∼150% in saturating indican but decreased ∼50% in saturating αMDG. Modeling indicated that the rate-limiting step for indican transport is sugar translocation, whereas for αMDG it is dissociation of Na+ from the internal binding sites. The inhibitory effects of indican on αMDG transport are due to its higher affinity and a 100-fold lower translocation rate. Our results indicate that competition between substrates and drugs should be taken into consideration when targeting transporters as drug delivery systems.
The Journal of Membrane Biology – Springer Journals
Published: Jul 1, 2008
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