Relations between substrate affinities and charge equilibration rates in the rat GABA cotransporter GAT1
| Autor: | Soragna, A., Bossi, Elena, Giovannardi, Stefano, Pisani, R., Peres, Antonio |
|---|---|
| Rok vydání: | 2004 |
| Předmět: |
EXPRESSION
XENOPUS-OOCYTES GABA Plasma Membrane Transport Proteins DNA Complementary Patch-Clamp Techniques GABA Agents Nipecotic Acids Molecular and Genomic Physiology TRANSIENT ELECTROGENIC PROPERTIES XENOPUS OOCYTES VOLTAGE-CLAMP CLONING EXPRESSION KINETICS AMINOBUTYRIC-ACID TRANSPORTER PRE STEADY-STATE CURRENTS COUPLED COTRANSPORTERS XENOPUS-OOCYTES GAT1 TRANSIENT MUTATION EXPRESSION Membrane Potentials CLONING Xenopus laevis COUPLED COTRANSPORTERS Animals Point Mutation RNA Messenger MUTATION KINETICS gamma-Aminobutyric Acid ELECTROGENIC PROPERTIES XENOPUS OOCYTES Valproic Acid Sodium PRE STEADY-STATE CURRENTS Membrane Transport Proteins Recombinant Proteins Rats Electrophysiology Solutions VOLTAGE-CLAMP GAT1 AMINOBUTYRIC-ACID TRANSPORTER |
| Zdroj: | The Journal of physiology. 562(Pt 2) |
| ISSN: | 0022-3751 |
| Popis: | The relations between apparent affinity for substrates and operating rates have been investigated by two-electrode voltage clamp in the GABA transporter rGAT1 expressed in Xenopus oocytes. We have measured the transport current induced by the presence of GABA, as well as the charge equilibration rate in the absence of the neurotransmitter, in various experimental conditions known to affect the transporter characteristics. The apparent affinities for GABA and for Na(+) were also determined in the same conditions. Two pharmacological actions and three mutated isoforms have been examined. In all cases significant correlations were found between the charge equilibration rates and apparent affinities for both substrates. In particular in the transport process, the apparent affinity for GABA appears to be inversely related to the sum of the unidirectional charge equilibration rates (alpha+beta), while the Na(+) apparent affinity is directly related to their ratio (beta/alpha). Together these observations suggest a kinetic basis for GABA affinity with higher turnover rates resulting in lower affinity, and indicate that an efficient uptake requires a compromise between these two parameters. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|
Plný text