Studies of viral DNA packaging motors with optical tweezers: A comparison of motor function in bacteriophages Φ29, λ, and T4

Douglas E. Smith, Derek N. Fuller, Dorian M. Raymer, Peter Rickgauer, Shelley N Grimes, Paul J Jardine, Dwight L. Anderson, Carlos E. Catalano, Vishal Kottadiel, Venigalla B. Rao

Research output: Chapter in Book/Report/Conference proceedingConference contribution


A key step in the assembly of many viruses is the packaging of double-stranded DNA into a viral procapsid (an empty protein shell) by the action of an ATP-powered portal motor complex. We have developed methods to measure the packaging of single DNA molecules into single viral proheads in real time using optical tweezers. We can measure DNA binding and initiation of translocation, the DNA translocation dynamics, and the filling of the capsid against resisting forces. In addition to studying bacteriophage Φ29, we have recently extended these methods to study the E. coli bacteriophages λ and T4, two important model systems in molecular biology. The three systems have different capsid sizes/shapes, genome lengths, and biochemical and structural differences in their packaging motors. Here, we compare and contrast these three systems. We find that all three motors translocate DNA processively and generate very large forces, each exceeding 50 piconewtons, ∼20× higher force than generated by the skeletal muscle myosin II motor. This high force generation is required to overcome the forces resisting the confinement of the stiff, highly charged DNA at high density within the viral capsids. However, there are also striking differences between the three motors: they exhibit differences in DNA translocation rates, degrees of static and dynamic disorder, responses to load, and pausing and slipping dynamics.

Original languageEnglish (US)
Title of host publicationOptical Trapping and Optical Micromanipulation IV
StatePublished - 2007
EventOptical Trapping and Optical Micromanipulation IV - San Diego, CA, United States
Duration: Aug 26 2007Aug 29 2007

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
ISSN (Print)0277-786X


OtherOptical Trapping and Optical Micromanipulation IV
Country/TerritoryUnited States
CitySan Diego, CA


  • Molecular motor
  • Optical tweezers
  • Single DNA manipulation
  • Viral assembly


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