The P22 tail machine at subnanometer resolution reveals the architecture of an infection conduit

Structure. 2009 Jun 10;17(6):789-99. doi: 10.1016/j.str.2009.04.006.


The portal channel is a key component in the life cycle of bacteriophages and herpesviruses. The bacteriophage P22 portal is a 1 megadalton dodecameric oligomer of gp1 that plays key roles in capsid assembly, DNA packaging, assembly of the infection machinery, and DNA ejection. The portal is the nucleation site for the assembly of 39 additional subunits generated from multiple copies of four gene products (gp4, gp10, gp9, and gp26), which together form the multifunctional tail machine. These components are organized with a combination of 12-fold (gp1, gp4), 6-fold (gp10, trimers of gp9), and 3-fold (gp26, gp9) symmetry. Here we present the 3-dimensional structures of the P22 assembly-naive portal formed from expressed subunits (gp1) and the intact tail machine purified from infectious virions. The assembly-naive portal structure exhibits a striking structural similarity to the structures of the portal proteins of SPP1 and phi29 derived from X-ray crystallography.

Publication types

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

MeSH terms

  • Bacteriophage P22 / chemistry*
  • Bacteriophage P22 / genetics
  • Bacteriophage P22 / metabolism*
  • Bacteriophage P22 / ultrastructure
  • Binding Sites
  • Capsid Proteins / chemistry
  • Capsid Proteins / genetics
  • Capsid Proteins / metabolism
  • Cryoelectron Microscopy
  • Crystallography, X-Ray
  • Models, Molecular
  • Protein Binding
  • Protein Conformation
  • Protein Structure, Secondary
  • Protein Structure, Tertiary
  • Protein Subunits / chemistry
  • Protein Subunits / genetics
  • Protein Subunits / metabolism
  • Viral Tail Proteins / chemistry*
  • Viral Tail Proteins / genetics
  • Viral Tail Proteins / metabolism*
  • Viral Tail Proteins / ultrastructure
  • Virion*


  • Capsid Proteins
  • Protein Subunits
  • Viral Tail Proteins
  • portal protein, bacteriophage P22