title: The calcium binding properties of phosphorylated and unphosphorylated cardiac and skeletal myosins.
abstract: 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.
mesh_terms: D000818:Animals; D001665:Binding Sites; D002118:Calcium; D007700:Kinetics; D009132:Muscles / Q000378:metabolism*; D009206:Myocardium / Q000378:metabolism*; D009218:Myosins / Q000378:metabolism; D009928:Organ Specificity; D010766:Phosphorylation; D011485:Protein Binding; D011817:Rabbits; D013552:Swine
chemical_list: D009218:Myosins; D002118:Calcium