FIGURE 4.

Mutations of voltage-sensing residues do not reduce the β2-induced enhancement of Ca²⁺ sensitivity. (A) Macroscopic current traces in 100 μM [Ca²⁺]_i of WT and mutant mSlo1 + β2ND. Test pulses were with 20-mV increments. Repolarization potentials for WT + β2, D153C + β2, R167A + β2, D186A + β2, and R213C + β2 channels were −160, −100, −100, −120, and −100 mV, respectively. (B) Mean G-V relationships of WT and mutant mSlo1 channels expressed with and without the β2ND-subunit in 0 and 100 μM [Ca²⁺]_i. G-V relationships are fit with the Boltzmann relation (solid line). (C) β2ND-induced V_1/2 shifts of WT and mutant channels in 100 μM [Ca²⁺]_i. (D) V_1/2 shifts from 0 to 100 μM [Ca²⁺]_i for WT and mutant channels with and without β2ND-subunit.