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The motor protein myosin-I produces its working stroke in two steps

Nature volume 398, pages 530–533 (1999)Cite this article

Abstract

Many types of cellular motility, including muscle contraction, are driven by the cyclical interaction of the motor protein myosin with actin filaments, coupled to the breakdown of ATP. It is thought that myosin binds to actin and then produces force and movement as it ‘tilts’ or ‘rocks’ into one or more subsequent, stable conformations1,2. Here we use an optical-tweezers transducer to measure the mechanical transitions made by a single myosin head while it is attached to actin. We find that two members of the myosin-I family, rat liver myosin-I of relative molecular mass 130,000 (Mr 130K) and chick intestinal brush-border myosin-I, produce movement in two distinct steps. The initial movement (of roughly 6 nanometres) is produced within 10 milliseconds of actomyosin binding, and the second step (of roughly 5.5nanometres) occurs after a variable time delay. The duration of the period following the second step is also variable and depends on the concentration of ATP. At the highest time resolution possible (about 1 millisecond), we cannot detect this second step when studying the single-headed subfragment-1 of fast skeletal muscle myosin II. The slower kinetics of myosin-I have allowed us to observe the separate mechanical states that contribute to its working stroke.

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Figure 1: Single-molecule mechanical interactions measured for myr-1 and skeletal-muscle myosin S1.
Figure 2: Averaging method to preserve amplitude of start and end of each interaction.
Figure 3: Averaged records of myosin binding to actin.

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Acknowledgements

We thank J. Kendrick-Jones for providing the skeletal myosin S1; A. F. Huxley and M. Peckham for helpful discussions and comments; the Royal Society, British Heart Foundation, American Cancer Society and the NIH for financial support. J.D.J. held a Howard Hughes Medical Institute fellowship.

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Authors and Affiliations

  1. Department of Biology, University of York, PO Box 373, York, YO10 5YW, UK

    Claudia Veigel, John C. Sparrow & Justin E. Molloy

  2. Boston Biomedical Research Institute, Boston, 02114, Massachusetts, USA

    Lynne M. Coluccio

  3. Department of Cell Biology, Scripps Research Institute, California, 92037, USA

    James D. Jontes & Ronald A. Milligan

Authors
  1. Claudia Veigel
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  2. Lynne M. Coluccio
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  3. James D. Jontes
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  4. John C. Sparrow
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  5. Ronald A. Milligan
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  6. Justin E. Molloy
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Correspondence to Justin E. Molloy.

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Veigel, C., Coluccio, L., Jontes, J. et al. The motor protein myosin-I produces its working stroke in two steps. Nature 398, 530–533 (1999). https://doi.org/10.1038/19104

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