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Inhibition of actin-activated myosin Mg(2+)-ATPase in smooth muscle by ruthenium red

F Nakamura1, M Naka, T Tanaka

  • 1Department of Molecular and Cellular Pharmacology, Mie University School of Medicine, Japan.

FEBS Letters
|December 7, 1992
PubMed

Insights

Ruthenium red inhibits smooth muscle myosin Mg(2+)-ATPase by binding to myosin heavy chain. This compound competes with actin for binding, impacting ATPase activation but not acto-myosin complex stability.

Area of Science:

  • Biochemistry
  • Molecular Biology
  • Muscle Physiology

Background:

  • Myosin Mg(2+)-ATPase is crucial for muscle contraction.
  • Actin-myosin interactions drive muscle force generation.
  • Understanding modulators of myosin ATPase activity is key to muscle function research.

Purpose of the Study:

  • To investigate the inhibitory mechanism of Ruthenium red on smooth muscle myosin Mg(2+)-ATPase.
  • To determine the binding site and interaction kinetics of Ruthenium red with myosin.

Main Methods:

  • Enzyme kinetics assays to measure Mg(2+)-ATPase activity.
  • Determination of inhibition constants (Ki) with respect to actin and ATP.
  • Assessment of acto-heavy meromyosin complex stability.

Main Results:

  • Ruthenium red competitively inhibited actin-activated myosin Mg(2+)-ATPase with respect to actin (Ki = 4.4 microM).
  • Ruthenium red non-competitively inhibited the ATPase with respect to ATP (Ki = 6.6 microM).
  • Ruthenium red bound to myosin heavy chain but not F-actin, and minimally dissociated the acto-heavy meromyosin complex.

Conclusions:

  • Ruthenium red directly interacts with the F-actin binding site on myosin heavy chain.
  • This interaction site is essential for ATPase activation, not for actin binding affinity.
  • Ruthenium red serves as a valuable tool for probing myosin function and actin-myosin interactions.

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