Figure 3. Cryo-EM structures of the AaLS variants.

(a–c) Cryo-EM density maps of AaLS-wt (a), AaLS-neg (b) and AaLS-13 (c) at 3.9, 5.4 and 5.2 Å resolution, respectively. Scale bars: 10 nm. (d–f) Dodecahedral, tetrahedral and icosahedral lattices matching the respective symmetries of AaLS-wt (d), AaLS-neg (e) and AaLS-13 (f). For AaLS-neg, two tetrahedral lattices (red and blue), embedded in a cube (grey), are depicted. (g–i) Close-up views of cryo-EM density maps of AaLS-wt (g), AaLS-neg (h) and AaLS-13 (i) around the three-fold rotational symmetry axes. Three pentamers from the refined models are shown as coloured ribbon diagrams. (j–l) 2D representation of the symmetry lattices for AaLS-wt (j), AaLS-neg (k) and AaLS-13 (l). Although the AaLS-neg structure is projected onto a flattened cube, note that it lacks the four-fold symmetry axes of a true cube because of the distinct pattern of pentamers on each face of the object and hence only possesses tetrahedral symmetry. The contact bars between two adjacent pentamers that have wt-like (pseudo) two-fold rotational symmetry are shown in red, while the other contact bars are shown in yellow. The asymmetric unit (ASU) for each structure is shown in the inset.