Cheng K H
Physics Department, Texas Tech University, Lubbock 79409.
Cancer Res. 1989 Dec 15;49(24 Pt 1):7026-30.
Using purified sarcoplasmic reticulum membranes as model systems, the role of calcium ion in the thermal inactivation of membrane calcium transport was investigated. Hyperthermia induces calcium release from the heavy fraction of sarcoplasmic reticulum. This calcium channel related calcium release was inhibited by the presence of glycerol and enhanced by the presence of ethanol. Calcium was found to protect the thermal-induced calcium transport inactivation of CaATPase in the light fraction of sarcoplasmic reticulum. Both glycerol and cholesterol protect the thermal inactivation of CaATPase. Yet their effects on the calcium-induced protection kinetics were rather different, i.e., the glycerol inserts its protection effect by increasing the degree of cooperativity of calcium binding, while cholesterol increases the calcium-binding affinity. The calcium protection effect was attributed to the ability of calcium to enhance the thermal stability of the protein. This was demonstrated by an upshift (30-39 degrees C) of the transition temperature of the rotational parameter of the native tryptophans of CaATPase in the presence of calcium.
以纯化的肌浆网膜作为模型系统，研究了钙离子在膜钙转运热失活中的作用。热疗可诱导肌浆网重质部分释放钙。这种与钙通道相关的钙释放受到甘油的抑制，并因乙醇的存在而增强。发现钙可保护肌浆网轻质部分中CaATPase的热诱导钙转运失活。甘油和胆固醇均能保护CaATPase的热失活。然而，它们对钙诱导的保护动力学的影响却大不相同，即甘油通过增加钙结合的协同程度来发挥其保护作用，而胆固醇则增加钙结合亲和力。钙的保护作用归因于钙增强蛋白质热稳定性的能力。这通过在钙存在下CaATPase天然色氨酸旋转参数的转变温度上移（30 - 39摄氏度）得到证明。
