Figure 7.

A463C decreases the apparent potassium affinity of the channel. Data were obtained from inside-out patches in symmetrical 140 mM NaCl. Currents were elicited by voltage steps to +100 mV followed by a step to −100 mV (A) or by voltage ramps from −100 to +200 mV (B). Internally applied potassium blocked the observed currents in a concentration-dependent manner. The data were quantified by measuring percent current block at +100 mV in either steps or ramps versus internal K⁺ concentration (•) or percent current block at −100 mV in step data (○). (C) The error bars represent SEM. A fit to the data with a single binding isotherm yields an approximate K _d of 6 mM.