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Structures of the Envelope and Tegument
All herpesviruses characterized to date share a characteristic multilay-
ered architecture (Fig. 3a), composed of a dsDNA genome, a portal-
containing icosahedral capsid shell, a thick, proteinaceous tegument
compartment, and a lipid bilayer envelope spiked with glycopro-
teins. 52-54 CryoET reconstructions of purified HSV-1 virions by
Grünewald et al . show pleomorphic or irregular oval shapes of the
viral envelope with the capsid eccentrically located near one pole 47
(Fig. 3b). The HSV-1 viral membranes are smooth and contain about
a dozen types of glycoprotein spikes, which appear to be more densely
packed around the pole distal from the capsid. 47 This distribution sug-
gests some sort of functional clustering that may help the virion
engage cell receptors during infection.
Fig. 3. Architecture of herpesvirus. ( a ) Basic architecture of the human her-
pesvirus virion. The dsDNA genome is coiled in the protein capsid. The capsid
is surrounded by inner and outer tegument protein layers. The envelope is a
host-derived lipid bilayer containing spikes of viral glycoproteins. ( b ) CryoET
structure of HSV-1 virion. A montage of different structures is shown, includ-
ing the envelope with glycoprotein (yellow), asymmetrical distribution of tegu-
ment densities (blue), and an averaged and icosahedrally symmetrized capsid.
Panel b was adapted with permission from the publisher and the authors. 47
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