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Dynamic polymorphism of single actin molecules in the actin filament

Nature Chemical Biology volume 2, pages 8386 (2006) | Download Citation

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Abstract

Actin filament dynamics are critical in cell motility1,2. The structure of actin filament changes spontaneously and can also be regulated by actin-binding proteins, allowing actin to readily function in response to external stimuli1. The interaction with the motor protein myosin changes the dynamic nature of actin filaments3,4. However, the molecular bases for the dynamic processes of actin filaments are not well understood. Here, we observed the dynamics of rabbit skeletal-muscle actin conformation by monitoring individual molecules in the actin filaments using single-molecule fluorescence resonance energy transfer (FRET)5,6,7 imaging with total internal reflection fluorescence microscopy (TIRFM)8. The time trajectories of FRET show that actin switches between low- and high-FRET efficiency states on a timescale of seconds. If actin filaments are chemically cross-linked, a state that inhibits myosin motility9, the equilibrium shifts to the low-FRET conformation, whereas when the actin filament is interacting with myosin, the high-FRET conformation is favored. This dynamic equilibrium suggests that actin can switch between active and inactive conformations in response to external signals.

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Acknowledgements

We thank A.H. Iwane and T. Wazawa for technical support and P. Karagiannis, J. West and M. Zulliger for revising the manuscript.

Author information

Author notes

    • Jun Kozuka
    •  & Hiroaki Yokota

    These authors contributed equally to this work.

Affiliations

  1. Formation of Soft Nanomachines, Core Research for Evolution Science and Technology, Japan Science and Technology Agency, Suita, Osaka, 563-0871, Japan.

    • Jun Kozuka
    • , Yoshiyuki Arai
    • , Yoshiharu Ishii
    •  & Toshio Yanagida
  2. Department of Biophysical Engineering, Osaka University, 1-3, Machikaneyama, Toyonaka, Osaka 560-8531, Japan.

    • Jun Kozuka
    • , Yoshiyuki Arai
    •  & Toshio Yanagida
  3. Department of Molecular Physiology, The Tokyo Metropolitan Institute of Medical Science, 3-18-22, Honkomagome, Bunkyo-ku, Tokyo 113-8613, Japan.

    • Hiroaki Yokota
  4. Soft Biosystem Group, Laboratories for Nanobiology, Graduate School of Frontier Biosciences, University of Osaka, 1-3, Yamadaoka, Suita, Osaka, 565-0871, Japan.

    • Toshio Yanagida

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Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Toshio Yanagida.

Supplementary information

PDF files

  1. 1.

    Supplementary Fig. 1

    Single-molecule FRET microscopy

  2. 2.

    Supplementary Fig. 2

    Power spectrum densities of the fluctuation of the fluorescence intensities and FRET efficiency.

  3. 3.

    Supplementary Fig. 3

    Evaluation of observed FRET signals using correlation factors.

  4. 4.

    Supplementary Fig. 4

    The effect of myosin-V in the absence of ATP on the FRET efficiency distribution.

  5. 5.

    Supplementary Fig. 5

    Kinetic analysis for the transition between two actin conformational states.

  6. 6.

    Supplementary Fig. 6

    Orthogonally polarized florescence measurement.

  7. 7.

    Supplementary Methods

  8. 8.

    Supplementary Data

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DOI

https://doi.org/10.1038/nchembio763

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