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Tropomyosin is essential for processive movement of a class V myosin from budding yeast

Alex R Hodges1, Elena B Krementsova, Carol S Bookwalter

  • 1Department of Molecular Physiology and Biophysics, University of Vermont, Burlington, VT 05405, USA.

Current Biology : CB
|June 19, 2012
PubMed

Insights

Yeast Myo2p, a motor protein, moves processively in vitro on actin tracks with tropomyosin. Tropomyosin is key to Myo2p

Area of Science:

  • Cell Biology
  • Biochemistry
  • Molecular Motors

Background:

  • Myosin V motors are actin-based and crucial for intracellular transport.
  • Previously, some class V myosins, like yeast Myo2p, were found to be nonprocessive in vitro.
  • Myo2p is essential in vivo for transporting organelles and vesicles.

Purpose of the Study:

  • To investigate the in vitro processivity of yeast Myo2p.
  • To determine the role of actin track composition in Myo2p processivity.
  • To identify factors that enable Myo2p to function processively.

Main Methods:

  • In vitro motility assays using purified Myo2p, actin, and tropomyosin.
  • Characterization of Myo2p's step size and duration of attachment.
  • Comparison of Myo2p behavior on bare actin versus actin-tropomyosin tracks.

Main Results:

  • Myo2p exhibits processive movement in vitro on actin tracks coated with tropomyosin.
  • Tropomyosin, particularly the Tpm1p isoform, significantly enhances Myo2p processivity.
  • Tropomyosin increases the motor's attachment time to actin by slowing MgADP release.

Conclusions:

  • Tropomyosin is essential for Myo2p to function as a processive motor in vitro.
  • This finding reveals a novel mechanism where tropomyosin switches a motor from nonprocessive to processive motion.
  • The results suggest Myo2p operates processively in vivo due to the presence of tropomyosin on actin cables.

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