Figure 3. H⁺ and transmitter binding.

• A
  Na⁺‐induced L‐glutamate uptake by purified EAAT1_CRYST reconstituted in liposomes loaded with K⁺. Choline (Ch⁺) condition was subtracted to the Na⁺ condition.
• B
  Log‐log plots of Na⁺ (red, n = 19) and L‐asp (blue, n = 27) K_D, as a function of pH at [Na⁺] = 0.5 mM. Na⁺ (n = 10) and L‐asp (n = 7) titration data at pH 7.4 and 9.0, respectively, are also reported in Fig 1. Solid lines are fits of straight lines.
• C
  Log‐log plots of L‐asp K_D for EAAT1_CRYST‐E406₃₈₆Q (light blue, n = 24) and EAAT1_CRYST‐Y405₃₈₅F (dark blue, n = 18), as a function of pH at [Na⁺] = 0.5 mM.
• D
  Potential H⁺‐bond network between protonated E406₃₈₆ (TM7b) and residues in HP2b in EAAT1_CRYST transmitter bound structure. HP2 is depicted in yellow and the ³⁹⁸NMDG motif in green. Residue numbering corresponds to EAAT1_WT, and the interatomic distance (angstrom) is parenthesis.

Data information: In (A) bar plots depict averages and s.e.m. values of three independent experiments (empty circles) performed in triplicate. In (B and C) symbols represent individual K_D values from n number of independent titrations.