Fig. 2.

Subtomogram averaging of the SARS-CoV-2 postfusion S. (A) Subtomogram averaging procedure, including the initial average of all particles at a binning level of eight (Left), the refined map at a binning level of two (Middle), and the postprocessed map with a local mask at the extracellular region at a binning level of two (Right). (B) The gold standard FSC curves for the final averaged map of postfusion S. (C) The directional FSC of the final averaged map of postfusion S. (D) Statistics of the coordinate and Euler angle changes before and after alignment during image processing. The coordinate offsets on the x, y, z axes are defined as dx, dy, and dz, while the angular offsets at three Euler angles are defined as drot, dtilt, and dpsi. (E) Plot back of the averaged map onto the original tomogram, showing relative orientations of postfusion Ss to the virus membrane. (F) Distribution of the tilting angles of postfusion Ss relative to viral envelope.