Pore radius profiles. (A) Pore hydration (transparent cyan color) in the closed and open pore conformations; only three protein subunits are shown (grey surface), and permeating potassium ions appear as green spheres. (B) Pore radius profiles of the PIP2-agonized crystal structure (PDB ID 3SPI), from a snapshot 2 µs into Sim. 1, and from a snapshot 5 µs into Sim. 2. Together, these profiles suggest a transition from the open, non-conducting conformation to a preactivated, semi-open pore conformation, and subsequently to a fully closed pore conformation. (C) Pore radius profile of the open-pore conformation obtained in simulations of the R178G activation gate mutant (Sim. 4) compared with the crystal structures in the presence (PDB ID 3SPI) and absence (PDB ID 3JYC) of PIP2, with preactivated, semi-open, and closed pore conformations. The pore radius profiles were generated using HOLE (Smart et al., 1996).
