Fig. 4.

Spatial association between TPPII and 26S proteasome. (A and B) Representative subtomograms containing TPPII particles colocalizing with 26S proteasomes. (Left column) Top-view particles. (Right column) Side-view particles. (Top row) Slices through the corresponding subtomograms and (Middle row) their isosurface representations. (Bottom row) The relative orientation of TPPII and 26S proteasome particles (averaged structures are used for better visualization). Red arrows point at TPPII, and black arrows point at the nearest 26S proteasomes. Dashed-line circles indicate the distance range for a single TPPII particle with a 55-nm radius (light blue) and twice the particle length with a 110-nm radius (dark blue). A and B indicate independent subtomograms. (C) Histogram of distances between TPPII and 26S proteasomes displaying the measured distances (blue line) and simulated distances (red line). The simulated distance distribution for random coordinate points include error bars that were obtained by calculating the mean and SDs for all 1,000 simulations (error bars refer to ±3σ SD). (D) Enlarged histogram area from C (dashed-line box). The dashed lines mark the 55 nm for a single TPPII particle length (light-blue dashed line) and the 110 nm for twice the particle length (dark-blue dashed line). (Scale bar: 50 nm.)