TABLE 2

Km and Vmax for TEA and MPP uptake by rOCT1 mutated at single amino acids within the presumed fourth TMH

Parallel measurements were performed with noninjected oocytes, oocytes expressing rOCT1 wild type, and oocytes expressing rOCT1 mutants. Uptake rates in oocytes expressing rOCT1 wild type or mutants were corrected for uptake in noninjected oocytes. The Michaelis-Menten equation was fitted to the data of individual experiments. Km and Vmax values calculated for mutants are presented as percentages of values that were measured in parallel for rOCT1 wild type. Mean ± S.E.M. values of three independent experiments are shown.

Mutants KmVmax
TEA MPP TEA MPP
V213G 432 ± 18* 279 ± 43* 66 ± 14 69 ± 8
G216A 90 ± 23 158 ± 62 8 ± 3** 17 ± 6**
W218F 81 ± 13 86 ± 19 46 ± 14 96 ± 10
S220I 193 ± 48 212 ± 56 41 ± 10* 67 ± 10
Y222F 31 ± 8* 112 ± 22 29 ± 3* 57 ± 11*
L224V 43 ± 17 53 ± 24 10 ± 4** 16 ± 3*
T226A 64 ± 18 33 ± 4* 48 ± 8 46 ± 3**
V229A 313 ± 68* 137 ± 34 56 ± 12 57 ± 15
  • * P < 0.05; ** P < 0.01, statistical significance of differences between wild-type and mutants.

  • P < 0.05, statistical significance between TEA and MPP uptake.