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Updated: Jul 8, 2026

Dissecting Mechanoenzymatic Properties of Processive Myosins with Ultrafast Force-Clamp Spectroscopy
09:38

Dissecting Mechanoenzymatic Properties of Processive Myosins with Ultrafast Force-Clamp Spectroscopy

Published on: July 1, 2021

She3p binds to the rod of yeast myosin V and prevents it from dimerizing, forming a single-headed motor complex

Alex R Hodges1, Elena B Krementsova, Kathleen M Trybus

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

The Journal of Biological Chemistry
|January 8, 2008
PubMed

Insights

Yeast myosin motors Myo2p and Myo4p are non-processive. The Myo4p adaptor protein She3p binds to Myo4p, forming a motor complex. This complex shows processivity when dimerized or when multiple motors move cargo, enabling mRNA transport.

Area of Science:

  • Molecular and Cell Biology
  • Biophysics
  • Cytoskeletal Motor Proteins

Background:

  • Vertebrate myosin Va is a dimeric processive motor protein involved in cargo transport along actin filaments.
  • Budding yeast possesses two class V myosins, Myo2p and Myo4p, which function as non-processive motors.
  • Previous studies indicated that the Myo4p motor domain, when fused to vertebrate myosin Va, exhibits processivity.

Purpose of the Study:

  • To investigate the functional properties of a novel myosin chimera comprising the Myo4p rod and tail with the mouse myosin Va motor and neck.
  • To elucidate the role of the adaptor protein She3p in the function and processivity of Myo4p.
  • To understand the mechanism underlying continuous mRNA transport by Myo4p-She3p in yeast.

Main Methods:

  • Construction and characterization of a myosin chimera (Myo4p rod/tail-Myosin Va motor/neck).
  • Biochemical analysis using sedimentation equilibrium and velocity assays to study myosin-She3p complex formation.
  • In vitro motility assays (ensemble and single-molecule) to measure ATPase activity, velocity, and processivity.
  • Dimerization of the myosin construct using a leucine zipper.

Main Results:

  • The adaptor protein She3p binds to the Myo4p rod region, forming a stable, single-headed myosin-She3p complex.
  • The myosin-She3p complex exhibits no processivity at the single-molecule level.
  • Dimerization of the myosin-She3p complex via a leucine zipper results in short processive runs.
  • Robust, continuous movement is observed when multiple monomeric myosin-She3p motors are attached to a quantum dot cargo.

Conclusions:

  • She3p acts as a subunit of the Myo4p motor, potentially forming a heterocoiled-coil structure.
  • The Myo4p-She3p motor complex requires dimerization or multimerization for processive movement.
  • Continuous mRNA transport in yeast is likely achieved through multiple high-duty-cycle Myo4p-She3p monomers or She2p-mediated dimerization.

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