Supplementary Figure 3: Cryo-EM analysis of the 26S human proteasome.

(a) Cryo-EM density maps of the human proteasome calculated with the C1 symmetry have an averaged resolution of 3.8 Å. Two perpendicular views are shown. The resolution range is color-coded. (b) Cryo-EM density maps of the RP calculated with a soft mask on the RP have an averaged resolution of 4.3 Å. (c) FSC curves of the three cryo-EM reconstructions: entire human proteasome with C2 symmetry (magenta), entire human proteasome with C1 symmetry (cyan), and the RP alone (green). (d) Angular distribution for the final reconstruction of the human proteasome with C2 symmetry. Each cylinder represents one view and the height of the cylinder is proportional to the number of particles for that view. The orientation preference is clearly seen. (e) FSC curves of the final refined model versus the overall 3.5 Å map (C2 symmetry) it was refined against (black); of the model refined in the first of the two independent maps used for the gold-standard FSC versus that same map (red); and of the model refined in the first of the two independent maps versus the second independent map (green). The small difference between the red and green curves indicates that the refinement of the atomic coordinates did not suffer from severe overfitting.