Three-dimensional structural dynamics of myosin V by single-molecule fluorescence polarization

Nature. 2003 Mar 27;422(6930):399-404. doi: 10.1038/nature01529.


The structural change that generates force and motion in actomyosin motility has been proposed to be tilting of the myosin light chain domain, which serves as a lever arm. Several experimental approaches have provided support for the lever arm hypothesis; however, the extent and timing of tilting motions are not well defined in the motor protein complex of functioning actomyosin. Here we report three-dimensional measurements of the structural dynamics of the light chain domain of brain myosin V using a single-molecule fluorescence polarization technique that determines the orientation of individual protein domains with 20-40-ms time resolution. Single fluorescent calmodulin light chains tilted back and forth between two well-defined angles as the myosin molecule processively translocated along actin. The results provide evidence for lever arm rotation of the calmodulin-binding domain in myosin V, and support a 'hand-over-hand' mechanism for the translocation of double-headed myosin V molecules along actin filaments. The technique is applicable to the study of real-time structural changes in other biological systems.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Actins / metabolism
  • Adenosine Triphosphate / metabolism
  • Animals
  • Brain
  • Calmodulin / metabolism
  • Chick Embryo
  • Fluorescence Polarization
  • Kinetics
  • Movement
  • Myosin Type V / chemistry*
  • Myosin Type V / metabolism*
  • Protein Binding
  • Protein Structure, Tertiary
  • Rabbits


  • Actins
  • Calmodulin
  • Adenosine Triphosphate
  • Myosin Type V