Correlation between Rtn4’s local density and ER membrane curvature intensity. (A) 3D data of Rtn4 localizations (green spheres) and a 3D surface based on Sec61β localizations (magenta-shaded surface). (B) 3D surface colored by mean curvature which ranges from −0.01 to 0.02 nm−1. (C) 3D surface colored by the local Rtn4 density within 50 nm of each vertex on the 3D surface ranging from 0 to 400 localizations. The blue arrowheads highlight locations on the surface that possess a high Rtn4 density nearby. (D) Histogram of the frequency of Rtn4 localizations occurring within 50 nm of a given vertex after normalizing for the frequency of the vertices' maximal principal curvatures (the curvature of the circular cross-section of the tubule). The hashed line represents the curvature where the Rtn4 density is the highest. The value above the hashed line represents the diameter of a hypothetical tubule with such a curvature. The scale bars represent 1 μm.
