Fig. 3. The Al binding site S_Al2.

a The extracellular view of the S_Al2 site in the ALMT1_M60A/Al/pH5 structure. b The S_Al1 site in the map of ALMT1_M60A/Al/pH5. The densities around the S_Al1 site and Ala60 are shown at the contour level of 4 σ. No density is observed around the S_Al1 site. c Al at the S_Al2 site is coordinated by Asp49, Glu156, Asp160, and two putative acetates. The green mesh show densities at the contour level of 5 σ, the magenta mesh shows densities at the contour level of 10 σ. Also see Supplementary information, Fig. S10h. d Concentration-dependent extracellular Al activation of WT and mutant AtALMT1. Data are reported as means ± SEM of at least five independent biological replicates. e The channel conductance of WT and mutant AtALMT1 measured at –180 mV. Data were analyzed by one-way ANOVA test. **P < 0.01, ***P < 0.001. Also see Supplementary information, Fig. S2a, e.