Fig. 3: Comparison of thiamine and pyridoxine binding in SLC19A2 and SLC19A3.

Binding affinity for SLC19A2 and SLC19A3 with thiamine at pH 7.5 (a) and pH 6.0 (b) and with pyridoxine at pH 6.0 (c) and pH 7.5 (d) measured using microscale thermophoresis (MST) assay (mean ± SEM, n = 3 independent experiments). Localization of thiamine in the inward-open SLC19A2 (e), pyridoxine in the outward-open SLC19A3 (g) and pyridoxine in the inward-open SLC19A2 structure (i). Detailed interactions between thiamine and SLC19A2 in the inward-open conformation (f), pyridoxine and SLC19A3 in the outward-open conformation (h) and pyridoxine and SLC19A3 in the outward-open conformation (j). Residues involved in thiamine and pyridoxine binding are depicted as sticks. Hydrogen bonds are indicated by blue dashed lines. k [³H] thiamine uptake activity of SLC19A2 mutants in stably transfected HEK 293 T cells. Data were normalized to WT and are presented as mean ± SEM of n = 3 biologically independent experiments. Statistical analysis was performed using two-tailed unpaired Student’s-tests. ****P ≤ 0.0001; EV, empty vector; WT, SLC19A2 wild type. l Summary of binding affinity via MST (mean ± SEM, n = 3 independent experiments).