TABLE 1.
Kinetic parameters of the acid amino acid-induced transport currents by EAAC1-WT and Met-367 mutants
The Km values (μm) and maximal current (Imax) for each of the shown substrates were obtained by oocytes expressing WT and the indicated mutants. The currents at −100 mV induced by various concentrations of the indicated substrate were measured in ND96-based medium, except for l-glutamate (SCN−), where 20 mm NaCl of the ND96 medium was replaced by the same concentration of NaSCN. Steady-state currents induced (EAAC1-WT) and/or inhibited (Met-367 mutants) by various concentrations of l-glutamate at +40mV were monitored, and the EC50 (EAAC1-WT) and IC50 (mutants) were calculated (see also Fig. 6). Imax is expressed as a percentage of the current induced by a saturating concentration of l-glutamate. The data analysis performed to determine the kinetic parameters is described under “Experimental Procedures.” The obtained parameters are based on data measured from at least three distinct experiments and represent the means ± S.E.
| Km of l-Glutamate | EC50/IC50 of l-Glutamate (SCN−) |
l-Aspartate |
d-Aspartate |
|||
|---|---|---|---|---|---|---|
| Km | Imax | Km | Imax | |||
| μm | ||||||
| WT | 13.0 ± 1.2 | 20.8 ± 4.0 | 15.0 ± 2.1 | 112 ± 6.5 | 8.2 ± 1.1 | 86 ± 3.7 |
| M367C | 134.2 ± 6.9 | 191.7 ± 12.8 | 33.5 ± 1.6 | 60.2 ± 5.7 | 156.3 ± 10.2 | 24.2 ± 2.2 |
| M367L | 132.1 ± 1.3 | 179.5 ± 39.9 | 27.2 ± 2.9 | 54.2 ± 2.1 | 79.3 ± 5.6 | 18.7 ± 1.3 |
| M367S | 177.4 ± 4.6 | 68.6 ± 7.5 | 17.9 ± 1.6 | 67.4 ± 1.1 | 100.6 ± 4.7 | 63.9 ± 4.1 |