Mechanism of force generation of a viral DNA packaging motor

Cell. 2005 Sep 9;122(5):683-92. doi: 10.1016/j.cell.2005.06.024.


A large family of multimeric ATPases are involved in such diverse tasks as cell division, chromosome segregation, DNA recombination, strand separation, conjugation, and viral genome packaging. One such system is the Bacillus subtilis phage phi 29 DNA packaging motor, which generates large forces to compact its genome into a small protein capsid. Here we use optical tweezers to study, at the single-molecule level, the mechanism of force generation in this motor. We determine the kinetic parameters of the packaging motor and their dependence on external load to show that DNA translocation does not occur during ATP binding but is likely triggered by phosphate release. We also show that the motor subunits act in a coordinated, successive fashion with high processivity. Finally, we propose a minimal mechanochemical cycle of this DNA-translocating ATPase that rationalizes all of our findings.

Publication types

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

MeSH terms

  • Adenosine Diphosphate / chemistry
  • Adenosine Diphosphate / metabolism
  • Adenosine Diphosphate / pharmacology
  • Adenosine Triphosphatases / chemistry
  • Adenosine Triphosphatases / physiology
  • Adenosine Triphosphate / chemistry
  • Adenosine Triphosphate / metabolism
  • Adenosine Triphosphate / pharmacology
  • DNA, Viral / drug effects
  • DNA, Viral / metabolism*
  • Kinetics
  • Molecular Motor Proteins / physiology*
  • Phosphates / chemistry
  • Phosphates / metabolism
  • Phosphates / pharmacology
  • Time Factors
  • Virus Assembly / drug effects
  • Virus Assembly / physiology*


  • DNA, Viral
  • Molecular Motor Proteins
  • Phosphates
  • Adenosine Diphosphate
  • Adenosine Triphosphate
  • Adenosine Triphosphatases