Analysis of corresponding mutations in type I and type III SUTs. (A) Substrate-induced currents in oocytes expressing type I sucrose transporter AtSUC1 wild type and AtSUC1(R163K). (B) LjSUT4 wild type, and LjSUT4(R169K). In A and B, currents were measured at −118 mV, pH 5.6, with a substrate concentration of 30 mM. Error bars indicate SE (n=3).