10.8 Virus-Associated Pyramids Atlas of Bacterial and Archaeal Cell Structure Home
Source: Veesler et al. (2013) Structure: PDB 3J31


As their name implies, STIV have icosahedral capsids with protruding turrets. The hexameric repeating unit in the shell is formed by three copies of a double-lobed protein, as you can see in this structure [91].

Virus-Associated Pyramids

Some archaeal phage make an even more dramatic exit, through virus-associated pyramids, or VAPs. You can see these escape hatches in this Sulfolobus solfataricus cell infected with Sulfolobus Turreted Icosahedral Virus (STIV) (⇩). The VAPs are made from a single phage-encoded protein that self-assembles into a seven-sided pyramid in the membrane. Note how the VAPs poke through and disrupt the cell’s surface layer. Note also the many, many copies the phage has made. We sometimes see storage granules inside VAPs, likely simply pushed there by excluding forces from the densely-packed nucleoid and assembling viral capsids in the center of the cell.

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