TABLE 1

Comparison of channel block and calculated ligand binding energies

For each blocking agent the first column shows for the indicated mutants IC50 values obtained at +50 mV in inside-out patches of X. laevis oocytes. The Hill coefficients of the corresponding dose-response curves were all in the range of 0.8 to 1.2 and are not shown here. The next column shows estimates for the changes in energy when mutants were introduced with a docked blocker molecule in place.

Clofilium Quinidine TBA
Mutant IC50 ΔEbind fl. ΔEbind ri. IC50 ΔEbind fl. IC50
nM (n) kcal/mol kcal/mol μM (n) kcal/mol μM (n)
hEAG1 0.79 ± 0.09 (5) 0.0 0.0 2.08 ± 0.36 (5) 0.0 1.15 ± 0.07 (4)
S436T 7.87 ± 0.76 (6) 9.5 −0.5 3.90 ± 0.80 (4) 5.1 68.4 ± 4.6 (5)
V437I 3.04 ± 0.41 (4) 1.5 0.6 5.77 ± 0.39 (6) 4.5 5.96 ± 0.25 (5)
S436T/V437I 30.0 ± 4.4 (6) 10.8 −0.7 27.2 ± 4.7 (6) 4.1 198 ± 23 (6)
A453S 4.67 ± 0.50 (5) 0.6 0.2 4.60 ± 1.27 (7) 0.1 1.97 ± 0.68 (5)
E1-c2 77.3 ± 19.2 (5) 55.6 ± 13.7 (7) 198 ± 33 (5)
E1-c2 TIS/SVA 7.90 ± 0.95 (6) 7.27 ± 0.41 (5) 12.5 ± 1.3 (5)
S433A 1.48 ± 0.20 (6) 0.31 ± 0.06 (5) 0.089 ± 0.011 (5)
S433C 0.60 ± 0.08 (5) 0.39 ± 0.01 (4) 0.29 ± 0.09 (5)

  • ΔEbind fl., energy for clofilium and quinidine at a position obtained from semiflexible docking shown in Fig. 4, a, right, and b; ΔEbind ri., energy for clofilium located at a position obtained after rigid docking (Fig. 4a, left).