The dehydration of calcium through the SF of TRPV6 and TRPV1. (A) The residues forming the SF of TRPV6. (B) The SF pore radius along the pore axis of the open-state TRPV6. The dashed curve is calculated from the cryo-EM structure. The solid line is the average pore radius from MD simulations, with the shaded area representing the standard error of the mean. (C) The total number (black) of coordinated oxygen atoms around the Ca²⁺ within the pore, and the contributions from protein (red) and water (blue), respectively. The significant contributions from protein oxygen are marked with corresponding protein residue IDs containing the oxygen (O: oxygen atom in the backbone; OD: oxygen atom at the side chain of aspartic acid; OE: oxygen atom at the side chain of glutamic acid). The solid lines represent the average values and the shaded areas represent the standard error of the mean from three independent simulators. The dashed straight lines indicate the boundaries of narrow pores with a radius <3 Å in the cryo-EM structure. (D–F) Similar to A–C, respectively, but for TRPV1.