Figure 3.

Selectivity of synthetic HB₁₂₈/polyP complexes for divalent cations over monovalent cations. (A) The figure shows selectivity of HB₁₂₈/polyP channels for Ca²⁺ over Na⁺. Single-channel current-voltage relations of HB₁₂₈/polyP complexes incorporated in planar lipid bilayers composed of synthetic 1-palmitoyl, 2-oleoyl, phosphatidylcholine and cholesterol (5:1; wt/wt) between asymmetric solutions: cis (ground) (65 mM CaCl₂, 10 mM NaCl, 5 mM MgCl₂, 10 mM Tris⋅Hepes, pH 7.4), and trans (ground) (200 mM NaCl, 0.1 mM CaCl₂, 5 mM MgCl₂, 10 mM Tris⋅Hepes, pH 7.4). The equilibrium potentials (calculated from concentration) were E_Ca = −82 mV, E_Cl = +9 mV, and E_Na is +76 mV. Error bars indicate standard deviation of the mean (n = 3). (B) Representative current traces of HB₁₂₈/polyP channels at +120 mV and −120 mV under the experimental conditions detailed in A. Data were filtered at 300 Hz. Note the difference in the current scales. The bars at the side of each profile indicate the fully closed state of the channel.