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Cryo-EM structure in situ reveals a molecular switch that safeguards virus against genome loss.

ABSTRACT: The portal protein is a key component of many double-stranded DNA viruses, governing capsid assembly and genome packaging. Twelve subunits of the portal protein define a tunnel, through which DNA is translocated into the capsid. It is unknown how the portal protein functions as a gatekeeper, preventing DNA slippage, whilst allowing its passage into the capsid, and how these processes are controlled. A cryo-EM structure of the portal protein of thermostable virus P23-45, determined in situ in its procapsid-bound state, indicates a mechanism that naturally safeguards the virus against genome loss. This occurs via an inversion of the conformation of the loops that define the constriction in the central tunnel, accompanied by a hydrophilic-hydrophobic switch. The structure also shows how translocation of DNA into the capsid could be modulated by a changing mode of protein-protein interactions between portal and capsid, across a symmetry-mismatched interface.

SUBMITTER: Bayfield OW

PROVIDER: S-EPMC7234808 | biostudies-literature | 2020 Apr

REPOSITORIES: biostudies-literature

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Cryo-EM structure in situ reveals a molecular switch that safeguards virus against genome loss.

Bayfield Oliver W OW Steven Alasdair C AC Antson Alfred A AA

eLife 20200414

The portal protein is a key component of many double-stranded DNA viruses, governing capsid assembly and genome packaging. Twelve subunits of the portal protein define a tunnel, through which DNA is translocated into the capsid. It is unknown how the portal protein functions as a gatekeeper, preventing DNA slippage, whilst allowing its passage into the capsid, and how these processes are controlled. A cryo-EM structure of the portal protein of thermostable virus P23-45, determined in situ in its ...[more]

PMID: 32286226

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