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Int. J. Mol. Sci. 2012, 13(12), 15565-15574; doi:10.3390/ijms131215565
Article

An Inverse Relationship Links Temperature and Substrate Apparent Affinity in the Ion-Coupled Cotransporters rGAT1 and KAAT1

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Department of Biotechnology and Life Sciences, University of Insubria, Via Dunant, 3, 21100 Varese, Italy
* Author to whom correspondence should be addressed.
Received: 19 October 2012 / Revised: 14 November 2012 / Accepted: 15 November 2012 / Published: 22 November 2012
(This article belongs to the Section Biochemistry, Molecular Biology and Biophysics)
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Abstract

The effects of temperature on the operation of two ion-coupled cotransporters of the SLC6A family, namely rat GAT1 (SLC6A1) and KAAT1 (SLC6A19) from Manduca sexta, have been studied by electrophysiological means in Xenopus laevis oocytes expressing these proteins. The maximal transport-associated current (Imax) and the apparent substrate affinity (K05) were measured. In addition to the expected increase in transport rate (Q10 = 3–6), both transporters showed greater K05 values (i.e., a decrease in apparent affinity) at higher temperatures. The transport efficiency, estimated as Imax/K05, increased at negative potentials in both transporters, but did not show statistically significant differences with temperature. The observation that the apparent substrate affinity is inversely related to the transport rate suggests a kinetic regulation of this parameter. Furthermore, the present results indicate that the affinities estimated at room temperature for mammalian cotransporters may not be simply extrapolated to their physiological operating conditions.
Keywords: transporter; temperature; affinity; rGAT1; KAAT1; electrophysiology transporter; temperature; affinity; rGAT1; KAAT1; electrophysiology
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Peres, A.; Vollero, A.; Margheritis, E.; D'Antoni, F.; Bossi, E. An Inverse Relationship Links Temperature and Substrate Apparent Affinity in the Ion-Coupled Cotransporters rGAT1 and KAAT1. Int. J. Mol. Sci. 2012, 13, 15565-15574.

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