Mechanism of the Apparent Inhibitory Effect of Mg2+ and Ca2+ on the Actomyosin MgATPase in Relation to the L2 Light Chain
In the past, several laboratories had observed that the actomyosin MgATPase activity was inhibited by micromolar concentrations of either Mg2+ or Ca2+ (Bullard et al, 1973; Murray, 1973; Lehman et al, 1974; Bremel and Weber, 1975; Pemrick, 1976). Although the L2 light chain was implicated (Pemrick, 1976), no mechanism was ever proposed for this cation sensitivity. The study reported in this chapter demonstrates that the “apparent” inhibitory effect of either Mg2+ or Ca2+ can be explained by an activating effect of free ATP, which requires a critical concentration of L2-containing actomyosin complexes.
KeywordsActomyosin ATPase Skeletal Myosin Heavy Meromyosin Actin Concentration Actomyosin Complex
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