Fig. 5.

Structural and functional analyses of human bestrophin1 (hBest1) Y236 and W287. a Population steady-state current density–voltage relationships in HEK293 cells expressing hBest1 Y236C with Cl⁻ in the external solution in the absence (gray) or presence (black) of 1.2 μM Ca²⁺ or with CH₃SO₃⁻ in the external solution in the absence (magenta) or presence (red) of 1.2 μM Ca²⁺, n = 5–6 for each point. b Population steady-state current density–voltage relationships in HEK293 cells expressing hBest1 Y236A with Cl⁻ in the external solution in the absence (gray) or presence (black) of 1.2 μM Ca²⁺, n = 7–8 for each point. *P < 0.05 compared to cells in the presence of Ca²⁺, using two-tailed unpaired Student’s t test. c Results from hBest1 W287F in the same format as a, n = 8–11 for each point. d Results from W287A in same format as b, n = 5 for each point. e Relative ion permeability ratios (P_CH3SO3/P_Cl) calculated from the Goldman–Hodgkin–Katz equation, n = 5 for each bar. f Relative ion conductance ratios (G_X/G_Cl) measured as slope conductance at the reversal potential plus 50 mV (CH₃SO₃⁻/Cl⁻, red) or minus 50 mV (Cl⁻/Cl⁻, black), n = 5–6 for each bar. g–i Visualization of the neck regions of KpBest Y211A (g), W252A (h), and W252F (i), showing critical residues on WT (yellow) and the mutants (green). Helices surrounding the critical residues (F70, P208, Y211, and W252) are labeled in the same colors as those in Fig. 4 for comparison. All error bars in this figure represent s.e.m.