Extended Data Fig. 7. Reversal potentials and ion-permeability ratios.

a,b, VUAA1-evoked whole-cell current from HEK293 cells expressing Orco with 150 mM intracellular CsCl and 150 mM extracellular NaCl (a, blue), or 100 mM extracellular CaCl₂ (b, red). c, Summary of reversal potentials (E_rev) and permeability ratios (P_ion/P_Cs) for wild-type and mutant Orco and Orco-OR complexes measured under bi-ionic conditions (mean ± s.d). E_rev were measured using N independent cells and corrected for the measured junction potential. P_ion/P_Cs were calculated from E_rev using Goldman-Hodgkin-Katz equations (see Methods) with their errors determined by propagation of the standard deviations. Three one-way ANOVA tests were performed using these E_rev data followed by Tukey-Kramer multiple comparison tests. (1) Orco selectivity of Na⁺, K⁺, Ca²⁺ and Mg²⁺ (P values are from comparisons to Na⁺ E_rev). (2) Wild-type and mutant Orco Na⁺ and Ca²⁺ selectivity (P values are from comparisons to wild-type Orco with the same ion, Na⁺ or Ca²⁺, as appropriate). (3) Orco homomer and Orco+OR heteromer Na⁺ and Ca²⁺ selectivity (P values are from comparisons to the Orco homomer with the same ion, Na⁺ or Ca²⁺, as appropriate). 245-T is 2,4,5-trimethylthiazole.