DNA crunching by a viral packaging motor: Compression of a procapsid-portal stalled Y-DNA substrate

Virology. 2010 Mar 15;398(2):224-32. doi: 10.1016/j.virol.2009.11.047. Epub 2010 Jan 12.


Many large double-stranded DNA viruses employ high force-generating ATP-driven molecular motors to package to high density their genomes into empty procapsids. Bacteriophage T4 DNA translocation is driven by a two-component motor consisting of the procapsid portal docked with a packaging terminase-ATPase. Fluorescence resonance energy transfer and fluorescence correlation spectroscopic (FRET-FCS) studies of a branched (Y-junction) DNA substrate with a procapsid-anchoring leader segment and a single dye molecule situated at the junction point reveal that the "Y-DNA" stalls in proximity to the procapsid portal fused to GFP. Comparable structure Y-DNA substrates containing energy transfer dye pairs in the Y-stem separated by 10 or 14 base pairs reveal that B-form DNA is locally compressed 22-24% by the linear force of the packaging motor. Torsional compression of duplex DNA is thus implicated in the mechanism of DNA translocation.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Bacteriophage T4 / physiology*
  • Capsid / metabolism*
  • DNA, Viral / metabolism*
  • Fluorescence Polarization
  • Fluorescence Resonance Energy Transfer
  • Fluorescent Dyes
  • Microscopy, Confocal
  • Nucleic Acid Conformation
  • Virus Assembly*
  • Xanthenes


  • DNA, Viral
  • Fluorescent Dyes
  • Xanthenes
  • Texas red