Fig. 4. AtSULTR4;1 STAS and TM interaction.

a Structure of AtSULTR4;1. The TM domain of one protomer is violet and teal (for the core and gate domains, respectively), and the STAS domain from the other protomer is pink. The boxes are enlarged in (b–d) to show the STAS-core and STAS-gate interactions, respectively. e SO₄²⁻ transport activities of charge-reversal mutants and the ΔSTAS construct. The height of the columns represents the average of 5–6 repeats from 2 batches of liposomes independently prepared. n = 5 for K353E, D547R, and D557R, and n = 6 for all others. Error bars indicate s.e.m. of the average. A two-tailed Student’s t test was applied to selected data. *** indicates p < 0.0001 compared to WT; ** indicates p < 0.001. Exact p values can be found in the Source Data file.