Voss J, Jones L R, Thomas D D
Department of Biochemistry, University of Minnesota Medical School, Minneapolis 55455.
Biophys J. 1994 Jul;67(1):190-6. doi: 10.1016/S0006-3495(94)80469-2.
The Ca-ATPase in the cardiac sarcoplasmic reticulum membrane is regulated by an amphipathic transmembrane protein, phospholamban. We have used time-resolved phosphorescence anisotropy to detect the microsecond rotational dynamics, and thereby the self-association, of the Ca-ATPase as a function of phospholamban phosphorylation and physiologically relevant calcium levels. The phosphorylation of phospholamban increases the rotational mobility of the Ca-ATPase in the sarcoplasmic reticulum bilayer, due to a decrease in large-scale protein association, with a [Ca2+] dependence parallel to that of enzyme activation. These results support a model in which phospholamban phosphorylation or calcium free the enzyme from a kinetically unfavorable associated state.
心肌肌浆网膜中的钙-ATP酶受一种两亲性跨膜蛋白——受磷蛋白调节。我们利用时间分辨磷光各向异性来检测钙-ATP酶的微秒级旋转动力学，从而检测其自缔合情况，该自缔合情况是受磷蛋白磷酸化和生理相关钙水平的函数。受磷蛋白的磷酸化增加了钙-ATP酶在肌浆网双层中的旋转流动性，这是由于大规模蛋白质缔合减少所致，其对[Ca2+]的依赖性与酶激活的依赖性平行。这些结果支持了一种模型，即受磷蛋白磷酸化或钙离子使酶从动力学上不利的缔合状态中释放出来。
