Figure 4.

Uptake of pyridoxine and thiamine by hSLC19A3 mutants in transiently transfected HEK293 cells: the effect of replacing hSLC19A3-specific amino acid residues in hTMDs 3, 4, and 6 with mSlc19a3 counterparts. All the transporters and mutants were tagged with EGFP at the N terminus. A, the specific uptake of [³H]pyridoxine (5 nM) was evaluated for 2 min at pH 5.5 and 37 °C. B, the specific uptake of [³H]thiamine (5 nM) was evaluated for 2 min at pH 7.4 and 37 °C. C, the uptake ratio was calculated by dividing pyridoxine uptake by thiamine uptake, using uptake values in percent of control. The uptake of pyridoxine and thiamine by hSLC19A3 as a control was 36.6 and 50.0 fmol/min/mg protein, respectively. Data are presented as means ± SD (n = 3). ∗p < 0.05 compared with control. EGFP, enhanced GFP; HEK293, human embryonic kidney 293 cell line; hSLC19A3, human solute carrier SLC19A3; hTMD, TMD in hSLC19A3; mSlc19a3, mouse Slc19a3; ND, not detected; TMD, transmembrane domain.