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Head-head and head-tail interaction: a general mechanism for switching off myosin II activity in cells

Hyun Suk Jung1, Satoshi Komatsu, Mitsuo Ikebe

  • 1Department of Cell Biology, University of Massachusetts Medical School, Worcester, Massachusetts 01655, USA.

Molecular Biology of the Cell
|May 23, 2008
PubMed

Insights

Myosin head interactions switch off muscle and nonmuscle cell activity. These intramolecular interactions block actin binding and ATPase activity, leading to relaxation and suppressed motility.

Area of Science:

  • Biochemistry
  • Molecular Biology
  • Cell Biology

Background:

  • Myosin molecules are crucial for cellular motility and muscle contraction.
  • Vertebrate smooth muscle myosin relaxation is linked to intramolecular head-head interactions.
  • The role of these interactions in other myosin types remains unclear.

Purpose of the Study:

  • To investigate if intramolecular head-head interactions are a general mechanism for switching off myosin II activity.
  • To examine myosin II from various muscle and nonmuscle sources.

Main Methods:

  • Single particle image processing of negatively stained myosin II molecules.
  • Electron microscopy analysis.

Main Results:

  • Head-head interactions, similar to smooth muscle, were observed in invertebrate striated and nonmuscle myosin II.
  • Surprisingly, vertebrate skeletal and cardiac muscle myosins also showed head-head interactions in relaxed states.
  • Conserved head-tail interactions were noted in all studied myosins, potentially contributing to the off-state.

Conclusions:

  • Intramolecular head-head and head-tail interactions are a general mechanism for myosin II regulation.
  • These interactions induce muscle relaxation and inhibit nonmuscle cell motility.
  • Myosin activation involves the disruption of these intramolecular interactions.

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