Na ⁺ binding and permeation pattern in the pore domain of TRPV6. (A) The contour plot of Na⁺ density on the R-z plane around TRPV6. (B) Side view of the three-dimensional Na⁺ density map. Only two subunits are shown for clarity. The ion density is shown as the magenta isosurface. The binding sites and key residues are labeled. The density threshold used to plot the sodium isosurface is 0.1 Å⁻³. (C) Evolution of the z coordinates of permeating Na⁺ through the TRPV6 channel. The boundaries of the narrow pore region are indicated by dashed lines. The z coordinates of each Na⁺ are shown in different colors. The grayscale of the narrow pore region indicates the amount of Na⁺ occupying the region, with darker colors indicating a larger amount of Na⁺.