Supplementary Figure 4: Cryo-EM density maps of individual subunits in the proteasome.

(a) Overall cryo-EM density maps of the α-ring in the CP calculated with C2 symmetry. Most notably, the central gate for substrate entry is closed, as evidenced by the relatively well-defined density maps at the gate. (b) Overall cryo-EM density maps of the β-ring in the CP calculated with C2 symmetry. The proteolytic chamber is empty. Representative cryo-EM density maps for the seven subunits α1 through α7 are displayed in panels c through i, respectively. Representative density maps for the seven subunits β1 through β7 are displayed in panels j through p, respectively. The side chain features are clearly identifiable in the density maps. (q) Cryo-EM density maps for the nine Rpn subunits in the lid (Rpn3, Rpn4, Rpn5, Rpn6, Rpn7, Rpn8, Rpn9, Rpn11, Rpn12, and Rpn15). For each of these Rpn subunits, the overall density maps are shown in the left, and the local maps for select secondary structural elements are shown in the right. (r) Cryo-EM density maps for the six Rpt subunits in the base (Rpt1 through Rpt6). For each of these Rpt subunits, the overall density maps are shown in the left, and the local maps for select secondary structural elements are shown in the right. The large and small AAA domains in each Rpt subunit are identified by magenta and green circles, respectively. (s) Cryo-EM density maps for three Rpn subunits in the base (Rpn1, Rpn2, and Rpn10).