Figure 2.

Mg²⁺ sensitivity of WT mslo1 and mutant channels at high [Mg²⁺]_i. (A) Current traces of WT mslo1 channels (left) and E374A:E399N mutant channels (right) recorded at indicated [Mg²⁺]_i and [Ca²⁺]_i. Testing potentials were −70 to 190 mV with 20-mV increments for WT mslo1 channels at 100 mM [Mg²⁺]_i and 0 [Ca²⁺]_i; and were −20 to 240 mV with 20-mV increments for others. The holding and repolarizing potentials were −80 and −50 mV, respectively. (B) Mean G-V relations of WT mslo1 (gray symbols) and E374A:E399N mutant channels (black symbols) at 0 or 100 mM [Mg²⁺]_i and 0 [Ca²⁺]_i, and fits with the Boltzmann relation (solid lines). (C) G-V shifts at 0 [Ca²⁺]_i from 0 to 10 mM [Mg²⁺]_i (gray bars) and from 0 to 100 mM [Mg²⁺]_i (black bars) of WT mslo1 and mutant channels E374A:E399N, E374Q and E399Q.