Figure 6.

Effect of cytosolic Mg²⁺ on the activation time course of SV currents. A and B, SV currents recorded at saturated cytosolic 10 mm Ca²⁺ (A) are compared with SV currents at saturated cytosolic 10 mm Mg²⁺ (B). For Mg²⁺ activation of SV currents, 10 μm CaCl₂ was added to the bath solution to saturate the proposed high-affinity Ca²⁺ binding site (see “Discussion”). Standard pipette and bath solutions (see “Materials and Methods”) were used with the addition of 10 mm CaCl₂ in A and with the addition of 10 mm MgCl₂ in B. C, Fitted time constants of the activation of SV currents plotted against the applied vacuolar membrane potentials (n = 3 vacuoles for each condition). Symbols are as in A and B.