Fig. 2.
Hierarchical assembly principle of αB oligomers is preserved in the phosphomimic αB-3E. (A) 3D reconstructions of αB-3E oligomers observed in cryo-EM. The isosurface threshold was set to enclose a molecular mass of 485 kDa for the 24-mer, 242 kDa for the 12-mer, and 121 kDa for the 6-mer. (B) 3D reconstructions of αB 24-, 12-, and 6-mer with the docked pseudoatomic models according to Braun et al. (17) superimposed (ribbon representation, domains colored as in Fig. 1A). Note that only the 24-mer pseudoatomic model is energy-minimized. 24-mers are viewed along a threefold symmetry axis intercepting the area harboring a window (open threefold area, 3o). Mass-rich domes surrounding 3o and accommodating the CTEs are highlighted by stars and threefold symmetric areas where the NTDs are located (closed threefold area, 3c) by closed arrows. 12-mers are viewed almost perpendicular to an axis that corresponds to the twofold symmetry axis of the 24-mer. The 6-mers are shown in three different orientations (top, side, and bottom views). All reconstructions are presented at a resolution of 18 Å to improve comparability. Note the consistency of the oligomer structures of αB-3E and αB-WT.