Extended Data Figure 2. Resolution estimation of cryo-EM 3D reconstruction.

a, The gold-standard FSC curve for the final cryo-EM 3D reconstruction generated with RELION1.3 (black) and EMAN2.1 (green). The overall resolution is 4.7 Å using the FSC cut-off = 0.143. b, Shown is the FSC curve between the cryo-EM density map generated with RELION1.3 and the molecular model (blue, FSC cut-off is 0.5) and the FSC curve between the 3D reconstructions generated with EMAN2.1 and RELION1.3 (red, FSC cut-off is 0.25). c, The cryo-EM density map of InsP₃R1 generated with RELION1.3 is colour-coded based on ResMap (Methods). The map is depicted as viewed along the membrane plane (left) or as a slab of the density (dashed box in left panel) coincident with the four-fold channel axis (right). The cryo-EM density map exhibits local resolution variation ranging from 3.6 Å to 6.5 Å with the most highly resolved densities in the TMD, while parts of the peripheral densities in the cytoplasmic region are of lower resolution. The low resolution peripheral density in the transmembrane region is attributed to detergent bound to the protein. d, Euler angle distribution of all particles used for the final 3D reconstruction. Each view is represented by a sphere, for which the size is proportional to the number of particles for this specific view.