Calcium binding to rabbit skeletal myosin under physiological conditions.
At a free Mg2+ concentration of 1.0 mM, myosin binds one Ca2+ per molecule when the Ca2+ concentration is 20 muM, a value in the concentration range expected during contraction of skeletal muscle. Mg2+ alters Ca2+ binding in a complex manner, not by simple competition. In the range from 20 to 100 muM Mg2+ it produces positive cooperativity between the high-affinity Ca2+ binding sites, in addition to shifting binding to higher Ca2+ concentrations. High-affinity Ca2+ binding is not significantly affected by the addition of ATP, increase in ionic strength to 0.1 and changes in temperature. Ca2+ binding did not increase actin-activated ATPase activity in the absence of regulatory proteins, but rather inhibited it.
D000199:Actins; D000818:Animals; D001665:Binding Sites; D002118:Calcium; D002614:Chelating Agents; D007700:Kinetics; D008274:Magnesium; D008433:Mathematics; D009119:Muscle Contraction; D009132:Muscles / Q000032:analysis; D009218:Myosins; D011485:Protein Binding; D011817:Rabbits
D000199:Actins; D002614:Chelating Agents; D009218:Myosins; D008274:Magnesium; D002118:Calcium