TABLE I.
Scheme 1 Parameters
| WT | WTA | WTB | E374A/E399N | |||||
|---|---|---|---|---|---|---|---|---|
| [Mg2+] (mM) | 0 | 10 | 100 | 10 | 100 | 0 | 10 | 100 |
| VhC (mV) | 156.2 | 139.1 | 120.1 | 139.1 | 120.1 | 142.9 | 135.3 | 118.4 |
| J0 × 102 | 2.77 | 4.10 | 6.34 | 4.10 | 6.34 | 3.76 | 4.47 | 6.60 |
| L0 × 106 | 1.06 | 1.08 | 2.57 | 1.08 | 2.57 | 1.66 | 1.31 | 4.16 |
| D | 24.4 | 52.2 | 68.8 | 48 | 55 | 25.9 | 27.7 | 23.0 |
Parameters for Eq. 1 that were varied to fit WT and E374A/E399N data in 0–100 mM Mg2+ (Fig. 5, A, B, C, and E). VhC in 10 and 100 mM were determined as VhC(0) + ΔVhC(Mg2+) where VhC(0) was determined from the 0 Mg2+ fit and ΔVhC(Mg2+) from gating current (Fig. 3 F). J0 is determined from VhC (J0 = exp(−VhCzJ/kT)). Charge parameters were fixed (zJ = 0.58 e, zJ = 0.30 e).