Human myosin Vc is a low duty ratio nonprocessive motor

Shinya Watanabe, Tomonobu M. Watanabe, Osamu Sato, Junya Awata, Kazuaki Homma, Nobuhisa Umeki, Hideo Higuchi, Reiko Ikebe, Mitsuo Ikebe*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

28 Scopus citations


There are three distinct members of the myosin V family in vertebrates, and each isoform is involved in different membrane trafficking pathways. Both myosin Va and Vb have demonstrated that they are high duty ratio motors that are consistent with the processive nature of these motors. Here we report that the ATPase cycle mechanism of the single-headed construct of myosin Vc is quite different from those of other vertebrate myosin V isoforms. KATPase of the actin-activated ATPase was 62 μM, which is much higher than that of myosin Va (∼1 μM). The rate of ADP release from actomyosin Vc was 12.7 s-1, which was 2 times greater than the entire ATPase cycle rate, 6.5 s-1. Pi burst size was 0.31, indicating that the equilibrium of the ATP hydrolysis step is shifted to the prehydrolysis form. Our kinetic model, based on all kinetic data we determined in this study, suggests that myosin Vc spends the majority of the ATPase cycle time in the weak actin binding state in contrast to myosin Va and Vb. Consistently, the two-headed myosin Vc construct did not show processive movement in total internal reflection fluorescence microscope analysis, demonstrating that myosin Vc is a nonprocessive motor. Our findings suggest that myosin Vc fulfills its function as a cargo transporter by different mechanisms from other myosin V isoforms.

Original languageEnglish (US)
Pages (from-to)10581-10592
Number of pages12
JournalJournal of Biological Chemistry
Issue number16
StatePublished - Apr 18 2008

ASJC Scopus subject areas

  • Molecular Biology
  • Biochemistry
  • Cell Biology


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