Thomas Klose in Michael Rossmann's laboratory at Purdue University determined the crystal structure of the major capsid protein of faustovirus. Faustovirus is a member of a new family of large dsDNA viruses that shares some similarity with members of the asfarviridae family. The outer capsid of this large virus is formed by 8280 copies of the major capsid protein and some minor proteins. Contrary to all other large dsDNA viruses, faustovirus does not surround its genome with an internal membrane, but instead has a second capsid layer that is composed of an unknown protein, which makes it likely that the virus utilizes different assembly and entry pathways than other large viruses. Along with determining the crystal structure of the capsid protein, the researchers reconstructed the whole virus using images from electron cryo-microscopy, and fit the structure of the major capsid protein into the EM map. This structure is the first step towards understanding these unusual viral processes and provides a foundation for further investigations. This is the largest viral capsid currently available in the PDB.
Structure of the faustovirus capsid. The outer shell is formed by 8280 copies of the major capsid protein. Individual monomers within a trimeric capsomer are colored in red, green, and purple. Holes visible at the fivefold vertices of the capsid are occupied by pentameric proteins in the complete virion, but the atomic structure of these proteins is unknown. The enlarged area on the right shows a side-view of a capsomer.
Klose T, Reteno DG, Benamar S, Hollerbach A, Colson P, La Scola B, Rossmann MG, "Structure of faustovirus, a large dsDNA virus," Proc. Natl. Acad. Sci. USA 113 (22), 6206-6211 (2016). DOI: 10.1073/pnas.1523999113