Viral architecture

Viral architecture
Functions of the virus particle = virion:
Genome protection (coating)
Receptor recognition and penetration into host cell
Genome uncoating and targeting Incorporation of enzymes (e.g., retroviruses)
An insight to the virion structure from a novelist…
…and the viral entities hidden within, submicroscopic parasites in their soviet socialist protein coats.
Don DeLillo “UNDERWORLD”
Principles of virion organization
Most virions resemble nuts with a genome inside and a protective protein shell outside
Small genome size dictates repeated use of
a small number of building blocks (protein
subunits)
Self-organization of repeated subunits results
in symmetrical structures Virion shape is determined by interactions
between protein subunits
Helical symmetry results in elongated virions
Helical capsid architecture
Organization of the protein
subunits (yellow) and RNA
(red) in a helical capsid
Beet yellows virus,
a 1,400 x 12 nm flexuous filament
Tobacco mosaic virus,
a 300 x 18 nm rod
Structure of the TMV capsid protein
Self-assembly of the TMV virion
Icosahedral symmetry results in roughly spherical virions
Virus proteins (VPs) 1, 2, and 3 share β-barrel fold
Poliovirus,
a 30 nm sphere
Structure of the icosahedral capsids
3-D structure of the capsid protein
Quasi-equivalent arrangement of the identical
protein subunits in a capsid Nodamura virus
Insect-infecting (+)RNA virus
Cryoelectron microscopy
Polio 32 nm
Adeno 110 nm
Papilloma 60 nm
Herpes 125 nm
Spherical RNA or DNA viruses that infect bacteria, fungi, plants, and animals often
share the similar, β-barrel type of a capsid
protein subunit(s)
Self-assembly of
the simple,
icosahedral virions
Assembly of the large icosahedral capsids
requires scaffolding proteins, which are
removed prior to DNA packaging
scaffold
DNA within
herpesvirus capsid
Helical, icosahedral, or combined virions can be complex
Geminivirus (ssDNA within a double sphere)
Atomic force microscopy used to visualize tails of the closterovirus (ssRNA + four proteins)
Tailed bacteriophages (dsDNA packed in heads): T4, T4, P2
Acquisition of a viral envelope
viral envelope
protein (transmembrane)
nucleocapsid
assembly
Viral genome (RNA or DNA)
capsid
protein
mature
progeny
virion
lipid bilayer
Surface of Herpes simplex virus modeled
using cryoelectron tomography
Glycoprotein
Membrane
Structure of Herpes simplex virus
Glycoprotein
Membrane
Tegument protein
Nucleocapsid
Protein-only capsids
Icosahedral Helical
JRC Picornavirus SF
Microviridae
Bromoviridae
Polyomaviridae
Adjoining Tymoviridae
Papillomaviridae
icosahedra
Tombusviridae
Parvoviridae
Geminiviridae Ourmiaviridae
Circoviridae
(JRC?)
Birnaviridae
Concentric icosahedra
JRC-DB Reoviridae
Adenoviridae
(JRC/non-JRC)
Other folds
Leviviridae
Picobirnaviridae
Totiviridae
Partitiviridae
Closteroviridae
Flexiviridae
Virgaviridae
Potyviridae
Inoviridae
Rudiviridae
Unknown folds
Caulimoviridae
Chrysoviridae
Complex
Spindle-shaped
Bicaudoviridae
Tailed bacteriophages
and archaeal viruses Caudovirales, GTA
Capsid-less
Viroids
Narnaviridae
Hypoviridae
Endornaviridae
Membrane-containing virions Inner membrane
Isosahedral capsid; JRC-DB
Corticoviridae, Tectiviridae
STIV
NCLDV: Outer membrane
Isosahedral Concentric icosahedra
Cystoviridae
Phycodnaviridae,
Mimiviridae
Arterivirida
Flaviviridae
Hepadnaviridae
Togaviridae
Herpesvirales
Double membrane
NCLDV
Asfaviridae
Ascoviridae
Iridoviridae
Polydnaviridae
Brick-shaped
Poxviridae
(NCLDV)
Droplet-shaped
Fuselloviridae
Guttaviridae
Bottle-shaped
Ampullaviridae
Pleomorphic virions,
thread-like nucleocapsid Mononegavirales
Orthomyxoviridae
Arenaviridae
Bunyaviridae
Coronaviridae
Ophioviridae
Roniviridae
Globuloviridae
Plasmaviridae
Irregular or cone-shaped nucleocapsid
Retroviridae
Helical nucleocapsid,
elongated virions
Lipothrixviridae
Filoviridae
Membrane-only
Pleolipoviruses
Baculoviridae
Nudivirus
Nimaviridae