Effect of the purified (Mg2+ + Ca2+)-activated ATPase of sarcoplasmic reticulum upon the passive Ca2+ permeability and ultrastructure of phospholipid vesicles.
Effect of the purified (Mg2+ + Ca2+)-activated ATPase of sarcoplasmic reticulum upon the passive Ca2+ permeability and ultrastructure of phospholipid vesicles.
复制标题
纯化的 (Mg2Ca2) 激活的肌浆网 ATP 酶对磷脂囊泡被动 Ca2 通透性和超微结构的影响。
DOI：
10.1016/s0021-9258(19)40973-3
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发表时间：
1975
期刊：
影响因子：
--
通讯作者：
T. Tillack
中科院分区：
文献类型：
--
作者：
R. Jilka;A. Martonosi;T. Tillack
破碎的肌浆网膜的被动Ca 2+渗透性比由天然或合成磷脂制备的脂质体的被动Ca 2+渗透性大10（4）至10（61）倍。通过将纯化的[Ca ~（2+）+Mg ~（2+）]激活的ATP酶掺入由不同磷脂制备的双层膜中，研究了膜蛋白对Ca ~（2+）渗透性的贡献。将Ca 2+转运ATP酶掺入脂相中增加了其Ca 2+渗透性，接近肌浆网膜的水平。渗透性变化可能是由于蛋白质环境中脂质相结构的重排引起的，或者可能代表蛋白质本身的特定性质。肌浆网钙结合蛋白没有产生类似的效果。Ca 2+从重组ATP酶囊泡中释放的速率增加不是载体介导的过程，如Ca 2+流出对Ca 2+浓度梯度的线性依赖性以及Ca 2+与其他二价金属离子之间不存在竞争和反向转运所示。在将转运ATP酶掺入脂相中时，增加的Ca 2+渗透性伴随着囊泡对蔗糖、Na+、胆碱和SO 42-的渗透性的类似增加，表明转运ATP酶不作为特异性Ca 2+通道。天然肌浆网膜是不对称的结构，冷冻蚀刻电子显微镜观察到的75-A颗粒主要位于外骨折面。在重构的ATP酶囊泡中，颗粒在两个断裂面之间的分布是均匀的，表明没有实现完全的结构重构。重组的ATP酶囊泡的Ca ~（2+）转运活性也远低于破碎的肌浆网。天然或重构囊泡负染色后可见的40-A表面颗粒的密度大于膜内颗粒的密度，这两种结构之间的关系仍有待建立。
The passive Ca2+ permeability of fragmented sarcoplasmic reticulum membranes is 10(4) to 10(61 times greater than that of liposomes prepared from natural or synthetic phospholipids. The contribution of membrane proteins to the Ca2+ permeability was studied by incorporating the purified [Ca2+ + Mg2+]-activated ATPase into bilayer membranes prepared from different phospholipids. The incorporation of the Ca2+ transport ATPase into the lipid phase increased its Ca2+ permeability to levels approaching that of sarcoplasmic reticulum membranes. The permeability change may arise from a reordering of the structure of the lipid phase in the environment of the protein or could represent a specific property of the protein itself. The calcium-binding protein of sarcoplasmic reticulum did not produce a similar effect. The increased rate of Ca2+ release from reconstituted ATPase vesicles is not a carrier-mediated process as indicated by the linear dependence of the Ca2+ efflux upon the gradient of Ca2+ concentration and by the absence of competition and countertransport between Ca2+ and other divalent metal ions. The increased Ca2+ permeability upon incorporation of the transport ATPase into the lipid phase is accompanied by similar increase in the permeability of the vesicles for sucrose, Na+, choline, and SO42- indicating that the transport ATPase does not act as a specific Ca2+ channel. Native sarcoplasmic reticulum membranes are asymmetric structures and the 75-A particles seen by freeze-etch electron microscopy are located primarily in the outer fracture face. In reconstituted ATPase vesicles the distribution of the particles between the two fracture faces is even, indicating that complete structural reconstitution was not achieved. The Ca2+ transport activity of reconstituted ATPase vesicles is also much less than that of fragmented sarcoplasmic reticulum. The density of the 40-A surface particles visible after negative staining of native or reconstituted vesicles is greater than that of the intramembranous particles and the relationship between these two structures remains to be established.