Kuriki Y, Halsey J, Biltonen R, Racker E
Biochemistry. 1976 Nov 16;15(23):4956-61. doi: 10.1021/bi00668a002.
The phosphorylation of (Na+, K+)ATPase from the electric organ of the electric eel is dependent on Mg2+. The amount of phosphoenzyme formed was increased by K+ and decreased by Na+. Kinetic analyses indicate that a ternary complex of ATPase, Pi and Mg2+ is formed prior to phosphorylation of the protein. Calorimetric studies revealed extraordinarily large enthalpy changes associated with the binding of Mg2+ (-49 kcal/mol) and of Pi (-42 kcal/mol), indicating a thermodynamically significant conformational change in the enzyme. The dissociation constant for the binding of Mg2+ and Pi derived from calorimetric measurements is in good agreement with the value obtained from the kinetic studies. These results indicate that ion binding induces a conformational change in the enzyme which is a prerequisite for phosphorylation by Pi.
电鳗电器官中（Na +，K +）ATP酶的磷酸化依赖于Mg2 +。形成的磷酸酶量因K +而增加，因Na +而减少。动力学分析表明，在蛋白质磷酸化之前形成了ATP酶、磷酸和Mg2 +的三元复合物。量热研究揭示了与Mg2 +（-49千卡/摩尔）和磷酸（-42千卡/摩尔）结合相关的极大焓变，表明该酶发生了热力学上显著的构象变化。通过量热测量得出的Mg2 +和磷酸结合的解离常数与动力学研究得到的值非常一致。这些结果表明离子结合诱导了酶的构象变化，这是磷酸进行磷酸化的先决条件。
