Figure 5. Divalent cation binding.

• A
  Superimposition of Rb⁺/Ba²⁺‐and Ba²⁺ bound EAAT1_CRYST structures with tranD is depicted in pink and green, respectively, and TM4 removed for clarity. Black mesh depicts anomalous‐difference map in the absence of Rb⁺ contoured at 4σ around the tranD, and inset shows details of Ba²⁺ coordination at Na3. Residue numbering corresponds to EAAT1_WT, and the coordination distance (angstrom) is parenthesis.
• B
  Ca²⁺ binding isotherms of EAAT1_CRYST at pH = 7.4 in the presence (pink) and absence (blue) of UPCH₁₀₁. Mutation D400₃₈₀N at Na3 strongly impairs Ca²⁺ binding (green). Symbols represent average and s.e.m. values of at least three independent experiments. Solid lines represent fits of Hill equation and dashed line is the fit in Fig 1C (blue line) corresponding to Na⁺ binding.
• C
  Log‐log plot of L‐asp K_D as a function of Ca²⁺ (n = 13).

Data information: in (B) symbols represent average and s.e.m. values of at least three independent titrations. In (C), blue symbols represent individual K_D values from n number of independent titrations.