Phosphorylation of porcine cardiac and rabbit skeletal myosins had no significant effect on their calcium binding properties, with both binding approximately 2 mol of Ca2+/mol of myosin.
Phosphorylation of cardiac and skeletal myosins does not significantly alter their calcium binding properties.
Porcine left ventricular cardiac myosin and rabbit white skeletal myosin were phosphorylated by rabbit skeletal myosin light chain kinase and their Ca2+ binding properties were examined by equilibrium dialysis techniques. No significant effect of phosphorylation on the Ca2+ binding properties of these myosins was observed. Both types of striated muscle myosins bound approximately 2 mol of Ca2+/mol of myosin with similar affinities of 3 x 10(7) M-1. In the presence of 3 x 10(-4) M Mg2+ the myosins bound Ca2+ with a reduced affinity of 3 to 4 x 10(5) M-1. Assuming competition between Mg2+ and Ca2+ for the binding sites on myosin, the changes in Ca2+ binding can be accounted for by a Mg2+ affinity of 2.5 to 3.0 x 10(5) M-1.
Holroyde et al. (Sun,) reported a other. Phosphorylation vs. Unphosphorylated myosin was evaluated on Ca2+ binding properties. Phosphorylation of porcine cardiac and rabbit skeletal myosins had no significant effect on their calcium binding properties, with both binding approximately 2 mol of Ca2+/mol of myosin.