The structure of an infectious P22 virion shows the signal for headful DNA packaging

Science. 2006 Jun 23;312(5781):1791-5. doi: 10.1126/science.1127981. Epub 2006 May 18.


Bacteriophages, herpesviruses, and other large double-stranded DNA (dsDNA) viruses contain molecular machines that pump DNA into preassembled procapsids, generating internal capsid pressures exceeding, by 10-fold, that of bottled champagne. A 17 angstrom resolution asymmetric reconstruction of the infectious P22 virion reveals that tightly spooled DNA about the portal dodecamer forces a conformation that is significantly different from that observed in isolated portals assembled from ectopically expressed protein. We propose that the tight dsDNA spooling activates the switch that signals the headful chromosome packing density to the particle exterior.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Bacteriophage P22 / genetics*
  • Bacteriophage P22 / physiology
  • Bacteriophage P22 / ultrastructure*
  • Capsid / chemistry
  • Capsid / ultrastructure*
  • Capsid Proteins / chemistry
  • Cryoelectron Microscopy
  • Crystallography, X-Ray
  • DNA Packaging*
  • DNA, Viral / analysis*
  • DNA, Viral / chemistry
  • Image Processing, Computer-Assisted
  • Nucleic Acid Conformation
  • Pressure
  • Protein Conformation
  • Virion / genetics
  • Virion / ultrastructure*


  • Capsid Proteins
  • DNA, Viral