Fig. 3.

The Lid domain and its effect on transport. a Electrostatic surface representation showing the negative cavity that connects the proton donor/acceptor site with the glucose binding site. A cluster of aromatic residues on the Lid domain isolate the proton site from the extracellular side. b Conservation of the aromatic residues of the Lid domain and residues of the proton donor/acceptor site and M1b. Both structure and sequence is colored according to sequence conservation between 1336 unique STPs (35–95% seq. ID) found across plant species. c Michaelis-Menten fit to glucose titration of STP10 mutant L43A at pH 4.0. d Glucose uptake rate as determined by a yeast uptake assay at different pH for WT STP10 and mutants C77A and C449A. Data for all assays are mean ± SD of three or more replicate experiments