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Nat Commun. 2017 Mar 13;8:14814. doi: 10.1038/ncomms14814.

Double-stranded RNA virus outer shell assembly by bona fide domain-swapping.

Author information

1
Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Roosevelt Drive, Oxford OX3 7BN, UK.
2
Department of Biosciences, University of Helsinki, Viikinkaari 9, Helsinki 00014, Finland.

Abstract

Correct outer protein shell assembly is a prerequisite for virion infectivity in many multi-shelled dsRNA viruses. In the prototypic dsRNA bacteriophage φ6, the assembly reaction is promoted by calcium ions but its biomechanics remain poorly understood. Here, we describe the near-atomic resolution structure of the φ6 double-shelled particle. The outer T=13 shell protein P8 consists of two alpha-helical domains joined by a linker, which allows the trimer to adopt either a closed or an open conformation. The trimers in an open conformation swap domains with each other. Our observations allow us to propose a mechanistic model for calcium concentration regulated outer shell assembly. Furthermore, the structure provides a prime exemplar of bona fide domain-swapping. This leads us to extend the theory of domain-swapping from the level of monomeric subunits and multimers to closed spherical shells, and to hypothesize a mechanism by which closed protein shells may arise in evolution.

PMID:
28287099
PMCID:
PMC5355851
DOI:
10.1038/ncomms14814
[Indexed for MEDLINE]
Free PMC Article

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