FIGURE 2.
Substrate-induced steady-state currents by EAAC1-WT and mutants. Steady-state currents induced by 5 mm of l-glutamate (circles), l-aspartate (squares), d-aspartate (triangles), or GABA (inverted triangles) are shown. As shown in Fig. 3, these are saturating concentrations for the substrates. The data were obtained from oocytes expressing either EAAC1-WT (A) or the indicated mutants (B–D) in a NaCl-based external medium (ND96), as described under “Experimental Procedures.” The membrane voltage was stepped from a holding potential of −25 mV to voltages between −100 and +40 mV in increments of +10 mV. Each potential was held clamped for 250 ms, followed by 250 ms of a potential clamped at −25 mV. Substrate-induced steady-state currents (Isubstrate − IND96) from 210 to 240 ms at each potential were averaged and normalized to the current induced by 5 mm l-glutamate at −100 mV (Inorm). These currents were than plotted against the corresponding potential (Vm (mV)). The data are the means ± S.E. of at least three repeats. The currents at −100 mV induced by 5 mm of l-glutamate ranged from −470 to −1320nA in the WT, from −450 to −760 nA in M367C, from −150 to −580 nA in M367S, and from −350 to −680 nA in M367L.