Buhle E L, Knox B E, Serpersu E, Aebi U
J Ultrastruct Res. 1983 Nov;85(2):186-203. doi: 10.1016/s0022-5320(83)90106-5.
Two-dimensional ordered arrays of the membrane-bound Ca2+ ATPase, were formed over a wide range of conditions (i.e., pH, ionic strength, temperature) in the presence of vanadate, and studied by electron microscopy and image processing. These ordered tubular and spherical membrane vesicles of Ca2+ ATPase could also be formed with approximately one bound ATP and between one and two nonchelatable Ca2+ bound. The tubular arrays ranged between 1 and 10 microns in length and had an average flattened diameter of 90 nm, as observed in negatively stained preparations. The basic building blocks of these ordered arrays appear to be linear ribbons of Ca2+ ATPase dimers. Fourier analysis of electron micrographs of these flattened tubes revealed a near-rectangular lattice (lattice angle 73.3 +/- 4.6 degrees with average lattice constants of a = 6.2 +/- 0.25 nm, and b = 11.5 +/- 0.30 nm). The double-stranded ribbons (i.e., parallel to a) are inclined by 56 +/- 3.7 degrees relative to the tube axis in a right-handed sense, as determined from freeze-dried metal-shadowed specimens. Computer averaging of negatively stained arrays reveals a crystallographic dimer of stain-excluding matter. The dimensions of each monomer within this dimer are consistent with established structural parameters, leading us to believe a form of the Ca2+ ATPase, capable of binding at least one ATP and of binding Ca2+ ions, may exist as a dimer in the sarcoplasmic reticulum.
在钒酸盐存在的情况下，在广泛的条件范围内（即pH值、离子强度、温度）形成了膜结合钙ATP酶的二维有序阵列，并通过电子显微镜和图像处理进行了研究。这些钙ATP酶的有序管状和球形膜囊泡也可以在结合约一个ATP以及结合一到两个不可螯合的钙离子的情况下形成。如在负染色制剂中观察到的那样，管状阵列的长度在1至10微米之间，平均扁平直径为90纳米。这些有序阵列的基本构建单元似乎是钙ATP酶二聚体的线性带。对这些扁平管的电子显微照片进行傅里叶分析，揭示了一个近乎矩形的晶格（晶格角为73.3±4.6度，平均晶格常数a = 6.2±0.25纳米，b = 11.5±0.30纳米）。从冷冻干燥的金属阴影标本确定，双链带（即平行于a）相对于管轴以右手方向倾斜56±3.7度。对负染色阵列进行计算机平均显示出一种不含染色质的晶体学二聚体。该二聚体内每个单体的尺寸与已确定的结构参数一致，这使我们相信，一种能够结合至少一个ATP并结合钙离子的钙ATP酶形式可能以二聚体的形式存在于肌浆网中。
