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![[Figure 4]](rr5238fig4mag.jpg)
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Figure 4
The effect of a polyhistidine affinity tag on the SARS-CoV-2 spike protein and β-galactosidase orientation distributions. The different parameters that are used to analyse the quality of the maps are shown next to the orientation plots. N indicates the number of particles used for reconstruction, R indicates the final resolution of the map, S indicates the sphericity and Eod indicates the efficiency of Fourier space coverage. (a) The locations of the tags on the protein models are indicated by black stars. The models used as references are PDB entries 8h3d and 6cvm for the spike protein and β-galactosidase, respectively. (b) The orientation-distribution plots of the spike protein change upon removal of the affinity tag, but the change is not sufficient to obtain an isotropic map. The addition of the cationic surfactant CTAB further alters the orientations of the spike protein without tag and leads to a more isotropic map. β-Galactosidase enzyme (bottom panel) orientations change upon removal of the affinity tag and lead to an isotropic high-resolution map without any additive. The unsharpened final combined maps are shown in grey in (b). |
![[Figure 4]](rr5238fig4.jpg)
 | STRUCTURAL BIOLOGY |
ISSN: 2059-7983
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