Summary of kinetic values of As(GS)3 transport by WT-MRP1, SF-MRP1, and Asn19/23Gln-MRP1–enriched membrane vesicles from HeLa and HEK293 cells prepared in the presence or absence of a phosphatase inhibitor cocktail (PIC)
| Km ± S.D. (μM) | aVmax ± S.D. (pmol mg−1 min−1) | N | |
|---|---|---|---|
| HeLa | |||
| WT-MRP1 | 0.32 ± 0.03* | 42 ± 17** | 4 |
| WT-MRP1 + PIC | 6.0 ± 1.3 | 505 ± 292 | 3 |
| SF-MRP1 | 0.3 ± 0.1* | 44 ± 15** | 5 |
| SF-MRP1 + PIC | 3.2 ± 1.4 | 609 ± 251 | 5 |
| HEK293 | |||
| WT-MRP1 | 3.8 ± 1.2 | 307 ± 118 | 8 |
| WT-MRP1 + PIC | 3.6 ± 0.8 | 270 ± 156 | 4 |
| SF-MRP1 | 0.6 ± 0.4* | 38 ± 21** | 4 |
| SF-MRP1 + PIC | 3.3 ± 1.8 | 195 ± 81 | 5 |
| N19/23Q-MRP1 | 0.5 ± 0.2* | 37 ± 9** | 3 |
| N19/23Q-MRP1 + PIC | 4.2 ± 1.6 | 300 ± 174 | 6 |
HEK, human embryonic kidney 293 (cell line); MRP1, multidrug resistance protein 1; SF, sugar-free; WT, wild-type.
↵a Vmax values were corrected for levels of WT-MRP1, SF-MRP1, and Asn19/23Gln relative to HEK-WT-MRP1 using densitometry (ImageJ Software) analysis of at least three different immunoblots (see Supplemental Table 2).
↵* Km value significantly different (P < 0.01) from HEK-WT-MRP1 (one way analysis of variance, Dunnett’s multiple comparison test).
↵** Vmax value significantly different (P < 0.01) than for HEK-WT-MRP1 (one way analysis of variance, Dunnett’s multiple comparison test).