Balzer H, Khan A R, Ristić-Radivojević S
Biochem Pharmacol. 1984 Jan 1;33(1):21-9. doi: 10.1016/0006-2952(84)90365-4.
The binding of calcium and magnesium ions to sarcoplasmic reticulum (SR) and chromaffin granule membranes was comparatively studied. The SR membranes are equipped with equal quantities of binding sites for both calcium and magnesium ions. The binding sites in presence of ATP combine specifically with calcium ions, while in the absence of ATP the binding sites react unspecifically with both ions. The trace amount of magnesium present in the SR membranes preparations is sufficient to drive ATP dependent calcium accumulation. Magnesium binding, however, is not affected by ATP. The chromaffin granule membranes bind calcium and magnesium in the same concentration range as observed for the SR membranes. Magnesium binding, however, is two times higher than that of calcium binding. In the absence of ATP, calcium and magnesium ions mutually compete. In the presence of ATP, magnesium binding values increase 3-5-fold, while the calcium binding isotherm remains unchanged. The appreciable contribution of the lipid phase to ions binding has been investigated, but was found to be of minor importance in this study.
对钙离子和镁离子与肌浆网（SR）及嗜铬颗粒膜的结合进行了比较研究。SR膜配备有等量的钙离子和镁离子结合位点。在ATP存在的情况下，结合位点与钙离子特异性结合，而在没有ATP时，结合位点与两种离子均发生非特异性反应。SR膜制剂中存在的微量镁足以驱动ATP依赖性钙积累。然而，镁的结合不受ATP影响。嗜铬颗粒膜结合钙和镁的浓度范围与SR膜相同。然而，镁的结合量是钙结合量的两倍。在没有ATP的情况下，钙离子和镁离子相互竞争。在ATP存在的情况下，镁结合值增加3至5倍，而钙结合等温线保持不变。已经研究了脂质相对离子结合的显著贡献，但在本研究中发现其重要性较小。
