Na ⁺ shows different permeation behavior in TRPV6 and TRPV1 in the presence of Ca ²⁺ . (A) Evolution of the z coordinates of TRPV6-permeating cations in the dicationic simulations. (B) Representative conformation during Na⁺ permeation of TRPV6. The backbone of protein is shown as a transparent cartoon. Residues forming the SF region are shown as licorice. Only two chains are shown for clarity. Ca²⁺ is shown as the pink sphere and Na⁺ as the yellow sphere. (C and D) C is similar to A and D is similar to B, but for TRPV1.