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J Biol Chem. 2020 Jan 3;295(1):1-12. doi: 10.1074/jbc.AC119.011196. Epub 2019 Oct 24.

The cryo-EM structure of African swine fever virus unravels a unique architecture comprising two icosahedral protein capsids and two lipoprotein membranes.

Author information

1
Centro de Biología Molecular Severo Ochoa, CSIC and Universidad Autónoma de Madrid, 28049 Madrid, Spain gandres@cbm.csic.es.
2
Molecular Recognition and Host-Pathogen Interactions Programme, CIC bioGUNE, CIBERehd, Bizkaia Technology Park, 48160 Derio, Spain.
3
Centro de Biología Molecular Severo Ochoa, CSIC and Universidad Autónoma de Madrid, 28049 Madrid, Spain.
4
NeCEN, Institute of Biology Leiden, Leiden University, 2333_CC Leiden, Netherlands.
5
Molecular Recognition and Host-Pathogen Interactions Programme, CIC bioGUNE, CIBERehd, Bizkaia Technology Park, 48160 Derio, Spain nabrescia@cicbiogune.es.
6
IKERBASQUE, Basque Foundation for Science, 48013 Bilbao, Spain.

Abstract

African swine fever virus (ASFV) is a complex nucleocytoplasmic large DNA virus (NCLDV) that causes a devastating swine disease currently present in many countries of Africa, Europe, and Asia. Despite intense research efforts, relevant gaps in the architecture of the infectious virus particle remain. Here, we used single-particle cryo-EM to analyze the three-dimensional structure of the mature ASFV particle. Our results show that the ASFV virion, with a radial diameter of ∼2,080 Å, encloses a genome-containing nucleoid surrounded by two distinct icosahedral protein capsids and two lipoprotein membranes. The outer capsid forms a hexagonal lattice (triangulation number T = 277) composed of 8,280 copies of the double jelly-roll major capsid protein (MCP) p72, arranged in trimers displaying a pseudo-hexameric morphology, and of 60 copies of a penton protein at the vertices. The inner protein layer, organized as a T = 19 capsid, confines the core shell, and it is composed of the mature products derived from the ASFV polyproteins pp220 and pp62. Also, an icosahedral membrane lies between the two protein layers, whereas a pleomorphic envelope wraps the outer capsid. This high-level organization confers to ASFV a unique architecture among the NCLDVs that likely reflects the complexity of its infection process and may help explain current challenges in controlling it.

KEYWORDS:

African swine virus; DNA viruses; cryo-electron microscopy; infection; nucleocytoplasmic large DNA viruses (NCLDV); structural virology; virus assembly; virus structure

Conflict of interest statement

The authors declare that they have no conflicts of interest with the contents of this article.

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