Extended Figure 4.

Masked classification scheme to look for rare conformations of the 70S IC and 70S EC. (a-c) The mask (grey) covering densities of IF1 (magenta), IF2 (purple), P/P-tRNA (orange) and P/E-tRNA is shown in different views. The views depict the position of the mask with respect to the 30S subunit (pale yellow) and the 50S subunit (blue). For the masked 3D classification scheme, this mask was applied to the dataset of refined 80,138 70S particles, which yielded mostly 3 types of classes (d). The first type of classes encompasses 44% of the particles with density for IF2 (purple) and tRNA in the P/I position (green), the second type of classes encompasses 48% with density for tRNA in the P/P position (orange), and the third type of classes encompasses ~8% without any density in the masked region. The 3D refinement of the first, second and third types of classes yielded cryo-EM maps of 70S IC, 70S EC and low-resolution 70S EC, respectively.