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Interdependence of factors affecting the actin-activated ATPase activity of myosin II from Acanthamoeba castellanii

J Kuznicki, E D Korn

    The Journal of Biological Chemistry
    |July 25, 1984
    PubMed

    Insights

    Phosphorylation significantly reduces Acanthamoeba myosin II

    Area of Science:

    • Biochemistry
    • Molecular Biology
    • Cell Biology

    Background:

    • Acanthamoeba myosin II is a key motor protein involved in cellular processes.
    • Myosin II activity is regulated by phosphorylation, affecting its interaction with actin.
    • Understanding these regulatory mechanisms is crucial for comprehending cell motility and contractility.

    Purpose of the Study:

    • To investigate the interdependent effects of phosphorylation and various assay conditions on Acanthamoeba myosin II's actin-activated ATPase activity.
    • To determine optimal conditions for measuring myosin II activity and identify factors influencing its function.

    Main Methods:

    • Enzyme kinetic assays were performed to measure actin-activated ATPase activity.
    • Varying concentrations of Mg2+, Ca2+, temperature, pH, and KCl were used.
    • The level of myosin II phosphorylation was systematically altered.

    Main Results:

    • Dephosphorylated myosin II exhibits maximal actin-activated ATPase activity.
    • Increasing phosphorylation levels decrease ATPase activity and increase optimal Mg2+ concentration.
    • Activity is highly sensitive to pH, temperature, and ionic strength, with optimal conditions identified near physiological parameters.

    Conclusions:

    • Phosphorylation is a critical regulator of Acanthamoeba myosin II activity, significantly reducing its actin-activated ATPase function.
    • Assay conditions, including Mg2+ concentration, pH, temperature, and KCl, profoundly influence myosin II activity.
    • The interdependence of these factors highlights the necessity of employing diverse conditions to accurately assess myosin II ATPase activity across different sources.

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