Effect of magnesium on the contractile behavior of actomyosin aggregates isolated from Physarum plasmodia.

The dependence on calcium concentration of the contractile behavior of actomyosin isolated from Physarum plasmodia according to Kohama & Kendrick-Jones (1986) was investigated under different magnesium conditions. The inhibitory calcium sensitivity is reduced at magnesium concentrations above or below 1 mM, i.e., contraction of actomyosin aggregates is most effectively inhibited in the presence of 1 mM calcium in combination with physiological magnesium concentrations. In the absence of calcium reactivation optimum is obtained at 8.5 mM Mg2+.