Figure 1.

Mutation E374A:E399N reduces Mg²⁺ sensitivity. (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 −20 to 240 mV with 20-mV increments. The holding and repolarizing potentials were −80 and −50 mV, respectively. (B) Mean G-V relations of WT mslo1 (gray symbols) and the mutant channels (black symbols) at 0 or 10 mM [Mg²⁺]_i and 0 [Ca²⁺]_i. G-V relations of these channels are fitted with the Boltzmann relation (solid lines, see MATERIALS AND METHODS). (C) Shift of G-V relations from 0 to 10 mM [Mg²⁺]_i at 0 [Ca²⁺]_i for WT mslo1 and the mutant channels. V_1/2 is the voltage where the G-V relation is at half maximum.