Fig. 4
From: Cryo-EM reveals ligand induced allostery underlying InsP3R channel gating
Detailed views of the selectivity filter in InsP3R1. a Sequence alignment for the P-loop region of selected InsP3R channels; the secondary structure elements are given above sequences; highly conserved residues within the signature sequence of the SF are coloured cyan; residues undergoing significant conformational changes are coloured yellow; D2551 within the SF, for which mutations can abolish Ca2+ conductance, is colored red; b EM densities with the corresponding models for the SF of Apo- (light purple) and AdA-InsP3R1 (green) are viewed from the cytosolic side. Cα atoms within the SF are depicted as spheres with the same colour code as in (a). c The SF (wire representation) from two opposing subunits is viewed from the side in Apo- (light purple) and AdA-InsP3R1 (green); distances between Cα atoms (spheres, colour-coded as in (a)) along the SF are indicated; d The surface electrostatic potential in the SF. Top panels show cross-sections along the 4-fold axis through the ion conduction pathway in Apo- (left) and AdA-InsP3R1 (right); lumenal entrance at the bottom. Bottom panels slices through the channel pore perpendicular to the 4-fold axis at the positions indicated with dashed lines in upper panels (viewed from lumen)
