Three kinds of currents in the canine betaine-GABA transporter BGT-1 expressed in Xenopus laevis oocytes |
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Authors: | Forlani G Bossi E Perego C Giovannardi S Peres A |
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Institution: | Laboratory of Cellular and Molecular Physiology, Department of Structural and Functional Biology, University of Insubria, Varese, Italy. |
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Abstract: | The cloned canine betaine-GABA cotransporter BGT-1 has been heterologously expressed in Xenopus laevis oocytes in order to characterize its electrophysiological properties. Voltage-clamp experiments on transfected oocytes reveal the presence of three types of membrane current which are absent in non-injected oocytes: (i) an organic substrate-independent current (uncoupled current); (ii) a transport-associated current, seen upon addition of betaine or GABA; (iii) presteady-state currents induced by voltage changes. The three kinds of current are analogous to those reported in structurally similar cotransporters. The transport-associated current is strictly dependent on the presence of Na(+). The good correlation between the amount of charge underlying the presteady-state currents and the transport-associated current indicates that both processes are due to the activity of the transporter. |
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