The motor domain determines the large step of myosin-V


Class-V myosin proceeds along actin filaments with large (36 nm) steps1,2,3. Myosin-V has two heads, each of which consists of a motor domain and a long (23 nm) neck domain. In accordance with the widely accepted lever-arm model4, it was suggested that myosin-V steps to successive (36 nm) target zones along the actin helical repeat by tilting its long neck (lever-arm)5. To test this hypothesis, we measured the mechanical properties of single molecules of myosin-V truncation mutants with neck domains only one-sixth of the native length. Our results show that the processivity and step distance along actin are both similar to those of full-length myosin-V. Thus, the long neck domain is not essential for either the large steps or processivity of myosin-V. These results challenge the lever-arm model. We propose that the motor domain and/or the actomyosin interface enable myosin-V to produce large processive steps during translocation along actin.

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Figure 1: Structure of the deletion mutant of myosin-V (M5IQ1rod).
Figure 2: Single-molecule measurement of displacements.
Figure 3: Records of displacements at a high ATP concentration of 2 mM.


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We are grateful to N. Jenkins for providing cDNA fragments of mouse myosin-V. We thank colleagues at the Single Molecule Processes Project, University of Massachusetts Medical School, and Osaka University for discussions, and J. West for critically reading the manuscript. This work was supported by grants from the National Institute of Health to M.I.

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Correspondence to Toshio Yanagida or Mitsuo Ikebe.

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Tanaka, H., Homma, K., Iwane, A. et al. The motor domain determines the large step of myosin-V. Nature 415, 192–195 (2002).

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