SCA of a high-conductance channel.

<p>(<b>A</b>) Current trace of a single high-conductance channel. The insertion event (marked by an asterisk) was registered at +10 mV and the applied voltage was then switched to −10 mV. The dashed line indicates the current level (zero) before insertion of the channel. The data in panels <b>A</b>, <b>B</b>, and <b>C</b> were collected using 3 M KCl as the electrolyte. (<b>B</b>) Current trace of the channel in response to the indicated voltage-ramp protocol. Note the near linear dependence of the current on the applied voltage. (<b>C</b>) Single channel currents in response to the indicated voltage-step protocol. (<b>D</b>) Dependence of the single channel conductance on the KCl concentration. After detection of a single channel insertion using 3 M KCl as bath solution (holding potential +10 mV), the electrolyte was diluted and registration of the current amplitudes of the same channel was conducted at 2.0 M and 1.0 M KCl, respectively. Data points are mean±SD for at least 4 independent measurements. (<b>E</b>) Current traces of a single channel in response to a low-speed linear increase (upper trace) or decrease (lower trace) of the holding potential. The bath solution contained 1.0 M NH₄Cl, 20 mM Tris-Cl, pH 7.8, and 2 mM DTT at both sides of the membrane. Note that the channel was still open even at hyperpolarizing holding potentials of ±150 mV. (<b>F</b>) Current-voltage relationship of the high-conductance channel under asymmetric salt conditions: 3.0 M KCl <i>trans</i>/1.5 M KCl <i>cis</i> compartment. The insertion of a single channel was detected at 3 M KCl at both sides of the membrane and at a voltage of +10 mV, then the electrolyte concentration in the <i>cis</i> compartment was decreased by dilution and an initial current recording was conducted at zero potential followed by stepwise (±10 mV) change of the applied voltage. Data points are mean±SD, n = 4–5. Bars in some cases are smaller than symbols.