Principles for enhancing virus capsid capacity and stability from a thermophilic virus capsid structure

Nat Commun. 2019 Oct 2;10(1):4471. doi: 10.1038/s41467-019-12341-z.


The capsids of double-stranded DNA viruses protect the viral genome from the harsh extracellular environment, while maintaining stability against the high internal pressure of packaged DNA. To elucidate how capsids maintain stability in an extreme environment, we use cryoelectron microscopy to determine the capsid structure of thermostable phage P74-26 to 2.8-Å resolution. We find P74-26 capsids exhibit an overall architecture very similar to those of other tailed bacteriophages, allowing us to directly compare structures to derive the structural basis for enhanced stability. Our structure reveals lasso-like interactions that appear to function like catch bonds. This architecture allows the capsid to expand during genome packaging, yet maintain structural stability. The P74-26 capsid has T = 7 geometry despite being twice as large as mesophilic homologs. Capsid capacity is increased with a larger, flatter major capsid protein. Given these results, we predict decreased icosahedral complexity (i.e. T ≤ 7) leads to a more stable capsid assembly.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacteriophages / genetics*
  • Bacteriophages / metabolism
  • Bacteriophages / ultrastructure
  • Capsid / chemistry
  • Capsid / metabolism*
  • Capsid / ultrastructure
  • Capsid Proteins / genetics*
  • Capsid Proteins / metabolism
  • Capsid Proteins / ultrastructure
  • Cryoelectron Microscopy
  • DNA, Viral / chemistry
  • DNA, Viral / genetics
  • DNA, Viral / ultrastructure
  • Genome, Viral / genetics*
  • Genomic Instability / genetics*
  • Hot Temperature
  • Models, Molecular
  • Thermus thermophilus / virology
  • Virion / chemistry
  • Virion / genetics*
  • Virion / ultrastructure
  • Virus Assembly / genetics


  • Capsid Proteins
  • DNA, Viral