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  • Title: Dual effect of Ca2+ on ultrasonic ATPase activity and polymerization of muscle actin.
    Author: Dancker P, Löw I.
    Journal: Biochim Biophys Acta; 1977 Sep 15; 484(1):169-76. PubMed ID: 142517.
    Abstract:
    Millimolar concentrations of Ca2+ stimulate actin polymerization whereas micromolar concentrations of Ca2+ depress polymerization. This latter effect leads to a reduction of ATPase (ATP phosphohydrolase, EC 3.6.1.3) activity of actin during sonication at low Mg2+ concentrations and in the absence of KCl. In the presence of KCl (90 mM) there is activation of ATPase activity by micromolar Ca2+ concentrations. These Ca2+ effects are half-maximal at a Ca2+ concentration of 2-10(-7) M. They can be explained by assuming that that ATPase activity is optimal in a medium range of actin polymer stability and that micromolar Ca2+ concentrations tend to labilize and depolymerize F-actin.
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