Table II. Terminal C-C carbon atom distances from residue sites and mutations to critical charged residues (indicated)

Distances determined during 10 ns of equilibration (Supplemental Fig. S1) are reported for the two states of the VSD. Values without se represent distances in the absence of key residue interactions and, hence, were not pursued further. Values in boldface highlight dominant spacings affecting charge interactions. Distances favoring the open channel (italic) and the closed channel (underlined) are indicated. Absolute electrostatic (Elec) and solvation energies (Sol) of the OPLS force field were calculated for the key residue interactions as indicated (Alves et al., 2007). The generalized Born energy for solvation was calculated according to Still et al. (1990). Note that using C-C distances adds 1 Å to the maximum for salt formation.

SiteMutationResidueDown (Open) StateUp (Closed) State
DistanceSalt Bridge?ElecSolDistanceSalt Bridge?ElecSol
ÅkJ mol−1ÅkJ mol−1
Asp-95Wild typeArg-1654.48 ± 0.08Yes−284 ± 6274 ± 520.47 ± 1.31
Arg-17114.89 ± 0.084.43 ± 0.06Yes−368 ± 13314 ± 6
Arg-17420.75 ± 0.834.62 ± 0.06Yes−388 ± 13313 ± 6
Arg-17724.92 ± 0.769.35 ± 0.07
D95EArg-1654.84 ± 0.16Yes−453 ± 14354 ± 819.52 ± 1.11
Arg-17115.08 ± 1.726.02 ± 0.06No−367 ± 11306 ± 5
Arg-17421.44 ± 1.235.06 ± 0.06No−403 ± 12328 ± 6
Arg-17726.08 ± 1.9312.91 ± 1.79
D95NArg-1654.40 ± 0.06No−59 ± 629 ± 419.51 ± 1.39
Arg-17115.07 ± 0.716.06 ± 0.06No−1 ± 30 ± 3
Arg-17421.14 ± 1.235.26 ± 0.06No−72 ± 460 ± 3
Arg-17725.25 ± 1.2810.56 ± 0.64
Asp-105Wild typeArg-16515.16 ± 0.0732.9 ± 1.4
Arg-17110.92 ± 0.06No−100 ± 199 ± 121.3 ± 0.7
Arg-17417.96 ± 1.0715.7 ± 0.7
Arg-17725.78 ± 0.9511.6 ± 0.6
D105EArg-16518.66 ± 1.0533.88
Arg-1717.99 ± 0.06No−244 ± 3239 ± 324.19
Arg-17416.10 ± 1.4615.83
Arg-17723.68 ± 0.9011.61
D105NArg-16517.67 ± 0.9933.36
Arg-1716.13 ± 0.57No2 ± 11−2 ± 1122.84
Arg-17414.34 ± 0.8214.48
Arg-17722.54 ± 1.2010.24
Asp-141Wild typeArg-16510.95 ± 0.0723.8 ± 1.36
Arg-1713.95 ± 0.05Yes−506 ± 14381 ± 513.4 ± 0.07
Arg-17411.97 ± 0.938.15 ± 0.07
Arg-17719.45 ± 0.923.53 ± 0.07Yes−389 ± 12354 ± 6
D141EArg-16513.24 ± 1.0125.5 ± 1.46
Arg-1715.27 ± 0.06No−374 ± 10314 ± 514.11 ± 0.51
Arg-17414.57 ± 1.4210.04 ± 0.35
Arg-17719.34 ± 0.875.28 ± 0.06No−473 ± 14383 ± 6
Arg-177Wild typeAsp-9525.29 ± 0.349.01 ± 0.08
Asp-10526.42 ± 0.4411.51 ± 0.11
Asp-14120.07 ± 0.464.13 ± 0.04Yes−389 ± 13354 ± 6
R177KAsp-9527.398.85 ± 0.09
Asp-10525.6711.27 ± 0.13
Asp-14119.914.81 ± 0.07Yes−332 ± 10287 ± 5