Figure 3. Cation binding sites in the TRPV6 pore.

a-b, Central slice (a) and top (b) views of crystal structure of rat TRPV6 (PDB ID: 5IWK) in surface representation, colored by electrostatic potential, with blue being positively charged, red negatively charged, and white neutral. c-h, Side (c,e,g) and top (d,f,h) views of the TRPV6 pore (the channel portion indicated by green dashed rectangles in a-b), with residues important for cation binding shown in stick representation. Front and back subunits in c, e and g are removed for clarity. Green, blue and pink mesh shows anomalous difference electron density for Ca²⁺ (c-d, 38–4.59 Å, 2.7σ; PDB ID: 5IWP), Ba²⁺ (e-f, 38–4.59 Å, 3.5σ; PDB ID: 5IWR) and Gd³⁺ (g-h, 38–4.59 Å, 7σ; PDB ID: 5IWT) and ions are shown as spheres of the corresponding color. Purple mesh shows simulated-annealing F_O-F_C electron density maps contoured at 4σ for Ca²⁺ (50–3.65 Å), 3σ for Ba²⁺ (50–3.85 Å) and 3.5σ for Gd³⁺ (50–3.80 Å). Adapted from (Saotome et al., 2016).