Table 3. Energetic parameters for the... | Rockefeller University Press

Table 3.

Energetic parameters for the HCN channel

Parameter	Parameter value
x_m (V → −∞) (V = −160 mV)^a	0.54 µM
x_m (V → ∞) (V = −30 mV)^a	1.72 µM
$- R T N_{\max} \ln (\frac{x_{m} \|_{V \to ∞}}{x_{m} \|_{V \to - ∞}}) + C_{F}$ ^b	−3.0 kcal/mol
ΔG_int (ligand pore)^c	−2.2 kcal/mol

Parameter	Parameter value
x_m (V → −∞) (V = −160 mV)^a	0.54 µM
x_m (V → ∞) (V = −30 mV)^a	1.72 µM
$- R T N_{\max} \ln (\frac{x_{m} \|_{V \to ∞}}{x_{m} \|_{V \to - ∞}}) + C_{F}$ ^b	−3.0 kcal/mol
ΔG_int (ligand pore)^c	−2.2 kcal/mol

The median ligand concentrations at very low and high voltages were approximated to the EC₅₀ values of the ligand binding curves reported in Kusch et al. (2010).

The interaction energy between the ligand binding domain and the rest of the protein and C_F is the correction factor (Eq. 31). The following limiting values were used in calculating C_F: P_O(V_min, x_min) = 0.58; P_O(V_min, x_max) = 1; P_O(V_max, x_max) = P_O(V_max, x_min) = 0.

The interaction between the ligand binding domains is the pore domain calculated from the HCN channel model parameters proposed in Kusch et al. (2012; equal to $- R T \ln (E_{5} / E_{1})$ ⁠; Fig. 4 A).

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