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GAT1 (GABA:Na+:Cl-) cotransport function. Database reconstruction with an alternating access model
1Department of Physiology, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas 75235-9040, USA. hilgeman@utsw.swmed.edu
The Journal of General Physiology
|September 2, 1999
Summary
A new alternating access transport model accurately describes gamma-aminobutyric acid (GABA) transporter 1 (GAT1) function, including ion and substrate binding and translocation.
Area of Science:
- Neuroscience
- Biophysics
- Molecular Biology
Background:
- Gamma-aminobutyric acid (GABA) transporter 1 (GAT1) is crucial for regulating GABAergic neurotransmission.
- Understanding the precise mechanism of GAT1 cotransport is essential for comprehending neuronal function and developing targeted therapeutics.
Purpose of the Study:
- To develop and validate an alternating access transport model for GAT1 cotransport.
- To elucidate the sequential binding and translocation steps of ions and GABA by GAT1.
Main Methods:
- Fitting various alternating access models to experimental data on GAT1 function in Xenopus oocyte membranes.
- Analyzing discrepancies between models and experimental data to refine the GAT1 transport mechanism.
Main Results:
- The developed model accurately simulates GAT1 current-voltage relations, substrate dependencies, and charge movements.
- The model highlights two predominant GAT1 states (Ein and Eout) and details ion/substrate binding and translocation pathways.
- The major electrogenic GAT1 reaction involves a conformational change between Ein and Eout states, rate-limiting GABA uptake.
Conclusions:
- The proposed alternating access model provides a comprehensive framework for GAT1 cotransport.
- This model successfully explains various experimental observations, including GABA-GABA exchange and transport in the absence of chloride.
- The findings offer insights into the molecular mechanisms underlying neurotransmitter transport.
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