Figure 3: Results from single-channel recordings.

(a) Representative current traces of NaKTs ion channel Na⁺ conductance at different TM potentials (internal solution: 20 mM HEPES, pH 7.5; 0.2 M NaCl and external solution: 20 mM MOPS, pH 4; 0.2 M NaCl; 5 mM CaCl₂). (b) I/V relationship of NaKTs ion channel in the presence of NaCl. The NaKTs ion channel Na⁺ conductance is 110 pS. (c) Representative current traces of NaKTs ion channel K⁺ conductance at different TM potentials (internal solution: 20 mM HEPES, pH 7.5; 0.2 M KCl and external solution: 20 mM MOPS, pH 4; 0.2 M KCl; 5 mM CaCl₂). (d) I/V relationship of NaKTs ion channel in the presence of KCl. The NaKTs ion channel K⁺ conductance is 88 pS. (e) Representative current traces of the NaKTs ion channel Na⁺ conductance as a function of Ca²⁺ in the external solution at a fixed membrane potential of −40 mV. (f) Open-channel probability of NaKTs ion channel, Po, as a function of Ca²⁺ in the external solution at a holding membrane potential of +40 mV (internal solution: 20 mM HEPES, pH 7.5; 0.2 M NaCl and external solution: 20 mM MOPS, pH 4; 0.2 M NaCl with CaCl₂ ranging from 250 μM to 20 mM). The error bars indicate the mean-square deviation from the average (fraction of open time over a total time interval) based on 3–5 separate time intervals. (g) Representative current traces of the chimeric NaKTs-SF_KcsA channel at 200 mM KCl with 0 mM CaCl₂. The single-channel conductance of the chimera is on the order of 300 pS.