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The anion conductance of the glutamate transporter EAAC1 depends on the direction of glutamate transport
Author(s) -
Watzke Natalie,
Grewer Christof
Publication year - 2001
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(01)02715-6
Subject(s) - glutamate receptor , chemistry , biophysics , conductance , glutamate aspartate transporter , ion transporter , steady state (chemistry) , transporter , excitatory amino acid transporter , membrane , biochemistry , biology , physics , receptor , condensed matter physics , gene
The steady‐state and pre‐steady‐state kinetics of glutamate transport by the neuronal glutamate transporter EAAC1 were determined under conditions of outward glutamate transport and compared to those found for the inward transport mode. In both transport modes, the glutamate‐induced current is composed of two components, the coupled transport current and the uncoupled anion current, and inhibited by a specific non‐transportable inhibitor. Furthermore, the glutamate‐independent leak current is observed in both transport modes. Upon a glutamate concentration jump outward transport currents show a distinct transient phase that deactivates within 15 ms. The results demonstrate that the general properties of EAAC1 are symmetric, but the rates of substrate transport and anion flux are asymmetric with respect to the orientation of the substrate binding site in the membrane. Therefore, the EAAC1 anion conductance differs from normal ligand‐gated ion channels in that it can be activated by glutamate and Na + from both sides of the membrane.