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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

Load and Pi control flux through the branched kinetic cycle of myosin V

Neil M Kad1, Kathleen M Trybus, David M Warshaw

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

The Journal of Biological Chemistry
|April 29, 2008
PubMed

Insights

Phosphate release and applied load influence myosin V motor protein stepping. Phosphate release acts as a checkpoint, controlling myosin V

Area of Science:

  • Molecular Biology
  • Biophysics

Background:

  • Myosin V is a crucial actin-based motor protein responsible for intracellular cargo transport.
  • Its processive stepping mechanism involves multiple 36-nm steps, but is sensitive to applied loads.

Purpose of the Study:

  • To investigate the role of phosphate (P(i)) release in myosin V's load-dependent stepping and detachment kinetics.
  • To elucidate the mechanism by which phosphate influences myosin V's interaction with actin.

Main Methods:

  • Utilized laser trap experiments to measure myosin V's stepping behavior under varying applied loads.
  • Analyzed the effect of 40 mm phosphate (P(i)) on motor protein kinetics.

Main Results:

  • Applied load slows myosin V stepping and increases backstep probability.
  • Phosphate (P(i)) reduces the load-dependence of both forward and backward steps.
  • P(i) release appears to commit myosin V to a load-dependent transition from an ADP-bound state.

Conclusions:

  • Myosin V detachment from actin can occur at two distinct cycle points.
  • Phosphate (P(i)) release and applied load act as checkpoints, regulating flux through parallel pathways.
  • A branched kinetic model explains the observed load- and phosphate-dependent behaviors of myosin V.

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