Apparent Km values of MPP+ and TEA+ transport mediated by rOCT1 wild-type and rOCT1 mutants
Initial uptake rates of nine different concentrations radioactively traced MPP+ or TEA+ were measured at 37°C in stably transfected HEK293 cells and apparent Km values were determined by fitting the Hill equation to data of individual experiments. Mean values ± S.D. of three or four separate experiments are shown. The compiled uptake measurements and the calculated Hill coefficients are shown in Figs. 3 and 4.
rOCT1 | Transport of MPP+ App. Km | Transport of TEA+ App. Km |
---|---|---|
µM | ||
WT | 4.7 ± 0.8 | 67 ± 9.9 |
F160A | 10.6 ± 0.9*** | 57 ± 8.3 |
F160Y | 13.3 ± 4.6*** | 84 ± 22 |
W218F | 5.0 ± 1.8 | 230 ± 28*** |
W218Y | 0.75 ± 0.09∆∆∆,# | 61 ± 7.2••• |
W218L | 11.9 ± 1.8***,••• | No uptake |
Y222F | 5.0 ± 1.8 | 55 ± 11 |
T226A | 8.8 ± 1.9∆∆ | 60 ± 7.7 |
R440K | 4.2 ± 1.0 | 32 ± 6.0∆∆ |
L447F | 3.1 ± 0.7 | 167 ± 23*** |
L447Y | 5.6 ± 1.5 | 80 ± 6.1□□□ |
D475E | 4.9 ± 2.0 | 19 ± 2.9*** |