CryoEM Density maps and atomic models that support the findings of this study have been deposited in the Electron Microscopy Database and the Protein Databank with the accession codes EMD-0000 (Whole particle reconstruction), EMD-0000 (Vertex Complex), EMD-00000 (Localized reconstruction of the penton region), EMD-00000 (Focused Classification of the penton region) and PDB ID 0Q0U (Atomic model of the asymmetric unit).  Funding Information ===================  This paper was supported by the following grants:  -   http://dx.doi.org/00.00000/000000000000Vetenskapsrådet 000-0000-000 to Janos Hajdu.  -   http://dx.doi.org/00.00000/000000000000Vetenskapsrådet 000-0000-0000 to Janos Hajdu.  -   http://dx.doi.org/00.00000/000000000000Vetenskapsrådet 000-0000-0000 to Janos Hajdu.  -   http://dx.doi.org/00.00000/000000000000Vetenskapsrådet 000-0000-0000 to Janos Hajdu.  -   http://dx.doi.org/00.00000/000000000000