Insight into DNA and protein transport in double-stranded DNA viruses: the structure of bacteriophage N4

J Mol Biol. 2008 May 2;378(3):726-36. doi: 10.1016/j.jmb.2008.02.059. Epub 2008 Mar 4.


Bacteriophage N4 encapsidates a 3500-aa-long DNA-dependent RNA polymerase (vRNAP), which is injected into the host along with the N4 genome upon infection. The three-dimensional structures of wild-type and mutant N4 viruses lacking gp17, gp50, or gp65 were determined by cryoelectron microscopy. The virion has an icosahedral capsid with T=9 quasi-symmetry that encapsidates well-organized double-stranded DNA and vRNAP. The tail, attached at a unique pentameric vertex of the head, consists of a neck, 12 appendages, and six ribbons that constitute a non-contractile sheath around a central tail tube. Comparison of wild-type and mutant virus structures in conjunction with bioinformatics established the identity and virion locations of the major capsid protein (gp56), a decorating protein (gp17), the vRNAP (gp50), the tail sheath (gp65), the appendages (gp66), and the portal protein (gp59). The N4 virion organization provides insight into its assembly and suggests a mechanism for genome and vRNAP transport strategies utilized by this unique system.

Publication types

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

MeSH terms

  • Bacteriophage N4 / enzymology
  • Bacteriophage N4 / metabolism
  • Bacteriophage N4 / ultrastructure*
  • Cryoelectron Microscopy
  • DNA, Viral / metabolism*
  • DNA, Viral / ultrastructure
  • DNA-Directed RNA Polymerases / metabolism*
  • Protein Transport
  • Viral Proteins / metabolism*


  • DNA, Viral
  • Viral Proteins
  • DNA-Directed RNA Polymerases