Insight into the Assembly of Viruses with Vertical Single β-barrel Major Capsid Proteins

Structure. 2015 Oct 6;23(10):1866-1877. doi: 10.1016/j.str.2015.07.015. Epub 2015 Aug 27.


Archaeal viruses constitute the least explored niche within the virosphere. Structure-based approaches have revealed close relationships between viruses infecting organisms from different domains of life. Here, using biochemical and cryo-electron microscopy techniques, we solved the structure of euryarchaeal, halophilic, internal membrane-containing Haloarcula hispanica icosahedral virus 2 (HHIV-2). We show that the density of the two major capsid proteins (MCPs) recapitulates vertical single β-barrel proteins and that disulfide bridges stabilize the capsid. Below, ordered density is visible close to the membrane and at the five-fold vertices underneath the host-interacting vertex complex underpinning membrane-protein interactions. The HHIV-2 structure exemplifies the division of conserved architectural elements of a virion, such as the capsid, from those that evolve rapidly due to selective environmental pressure such as host-recognizing structures. We propose that in viruses with two vertical single β-barrel MCPs the vesicle is indispensable, and membrane-protein interactions serve as protein-railings for guiding the assembly.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Archaeal Viruses / genetics
  • Archaeal Viruses / metabolism
  • Archaeal Viruses / ultrastructure*
  • Binding Sites
  • Capsid / metabolism
  • Capsid / ultrastructure*
  • Capsid Proteins / chemistry*
  • Capsid Proteins / genetics
  • Capsid Proteins / metabolism
  • Cryoelectron Microscopy
  • Crystallography, X-Ray
  • Disulfides
  • Escherichia coli / genetics
  • Escherichia coli / metabolism
  • Gene Expression
  • Genome, Viral*
  • Haloarcula / virology
  • Models, Molecular
  • Protein Binding
  • Protein Multimerization
  • Protein Structure, Secondary
  • Protein Structure, Tertiary
  • Recombinant Proteins / chemistry
  • Recombinant Proteins / genetics
  • Recombinant Proteins / metabolism
  • Salt Tolerance
  • Virion / genetics
  • Virion / metabolism
  • Virion / ultrastructure*
  • Virus Assembly*


  • Capsid Proteins
  • Disulfides
  • Recombinant Proteins