Figure 3. The structure of the C-terminal extension of the S subunit.

(a) EM density map of the unsharpened CPMV-B map with colours as described previously. In yellow is the C terminus of CPMV-B (amino acids 184–189), which follows the same path as the current atomic model (PDB 1NY7⁴). The final C-terminal amino acids (190–213) are missing from both the crystal structure and the CPMV-B EM density map. (b) EM density map of the unsharpened eVLP map with colours as described previously. The density corresponding to amino acid 184–189 is coloured yellow. Although this section of the EM density is too weak to allow a polypeptide backbone to be built, we can clearly see this portion of the C-terminal moves in the eVLP map compared with the CPMV-B map (see yellow segment in a). Coloured magenta is the newly resolved 13-amino acid residue (190–202 in the S subunit). (c) Zoomed-in version of the C-terminal extension from the sharpened EM density. The new atomic model is shown inside.