The birnavirus crystal structure reveals structural relationships among icosahedral viruses

Cell. 2005 Mar 25;120(6):761-72. doi: 10.1016/j.cell.2005.01.009.


Double-stranded RNA virions are transcriptionally competent icosahedral particles that must translocate across a lipid bilayer to function within the cytoplasm of the target cell. Birnaviruses are unique among dsRNA viruses as they have a single T = 13 icosahedral shell, lacking the characteristic inner capsid observed in the others. We determined the crystal structures of the T = 1 subviral particle (260 angstroms in diameter) and of the T = 13 intact virus particle (700 angstroms in diameter) of an avian birnavirus to 3 angstroms and 7 angstroms resolution, respectively. Our results show that VP2, the only component of the virus icosahedral capsid, is homologous both to the capsid protein of positive-strand RNA viruses, like the T = 3 nodaviruses, and to the T = 13 capsid protein of members of the Reoviridae family of dsRNA viruses. Together, these results provide important insights into the multiple functions of the birnavirus capsid and reveal unexpected structural relationships among icosahedral viruses.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Birnaviridae / chemistry*
  • Capsid / chemistry
  • Capsid Proteins / chemistry*
  • Computer Simulation
  • Crystallization
  • Evolution, Molecular*
  • Models, Molecular*
  • Molecular Sequence Data
  • Protein Subunits / chemistry
  • Reoviridae / chemistry*


  • Capsid Proteins
  • Protein Subunits

Associated data

  • PDB/1WCD
  • PDB/1WCE