Table 1.

Altered substrate and inhibitor selectivity of mutant ASCT1 and ASCT2 transporters

	ASCT1	A1-T459C	A1-T458S	A1-T458S/T459C	ASCT2	A2-S481T/S482C
L-Ser EC50 (μM)	100 ± 20	83 ± 6	106 ± 4	45 ± 5	250 ± 40	61 ± 7
L-Gln EC50 (μM)	–	260 ± 80	–	90 ± 10	80 ± 10	–
GPNA % inhibition	26 ± 3	18 ± 1	ND	41 ± 4	90 ± 5	20 ± 3

To establish EC₅₀s, varying concentrations of L-serine or L-glutamine was applied in a NO₃ ⁻-containing buffer, and the current (I) at + 60 mV measured. EC₅₀ values of L-serine were competed against 1 mM GPNA to determine the level of inhibition. Currents generated in the presence of inhibitor were subtracted from currents generated in the absence of inhibitor to determine % inhibition. All values represent mean ± S.E.M (n ≥ 3). A dash indicates the substrate did not generate currents; ND indicates the value was not determined.