Fig. 5.

Molecular simulations in the presence of electric field shows an upward displacement of the BK gating charges. (A and B) z Axis displacement of the guanidine group CZ atom as a function of time for (A) Arginine 210 and (B) Arginine 213. Events are plotted for the entire ∼3.9-µs MD simulations under an external electric field (+400 mV). Each color represents the arginine from an individual sensor of the BK channel, and an all-points histogram of the last 500 ns is shown to the right of each panel for better visualization of the final position of the gating charge. The plot shows that both R210 and R213 tend to raise their position in each sensor about 4 Å in the case of R210 and 2 Å in the case of R213. Vertical magenta dashed lines indicate the moment in which the electric field began to be applied during the simulation. (C) BK VSD in the resting state obtained from a simulation under equilibrium in the absence of electric field. R207 is interacting with D153, while both R210 and R213 are in contact with D186. (D) BK VSD in the active state obtained after 3 µs of MD simulation under an external electric field (+400 mV). R210 and R213 move up; thus, R210 now appears to be interacting with D153, while R213 makes interactions with F160 and D186.