Figure 5

Knock–off mechanism of Ca²⁺ permeation. (a–f) Sequential representative positions of Ca²⁺ ions in the C7.1 simulation in (a,d) initial configuration, (b,e) transition state, and (c,f) final configuration. Blue, magenta and mustard spheres (a–c) represent incoming, intermediate and leaving Ca²⁺ ions, respectively. Similarly colored mesh surfaces (d–f) represent spaces occupied by the corresponding ions throughout the simulation. Residues D541, T538, and M569 are shown in stick representation. (g) Ca²⁺ ion trajectories along z-axis during C7.1 simulation. The vertical red dashed lines indicate states #1–3 illustrated in (a,d), (b,e), and (c,f) respectively. The horizontal red dashed line indicates the level of ion crossing into the channel.