Herbette L G, MacAlister T, Ashavaid T F, Colvin R A
Biochim Biophys Acta. 1985 Feb 14;812(3):609-23. doi: 10.1016/0005-2736(85)90254-8.
The morphological and ultrastructural properties of highly purified canine cardiac sarcolemmal vesicles, prepared by a modification (Colvin, R.A., Ashavaid, T.F. and Herbette, L.G. (1985) Biochim. Biophys. Acta 812, 601-608) of the method of Jones et al. (Jones L.R., Madlock, S.W. and Besch, H.R. (1980) J. Biol. Chem. 255, 9971-9980), were examined by several techniques. Thin-section electron microscopy showed predominantly intact unilamellar vesicles with little staining beyond the lipid bilayer boundaries. Freeze-fracture electron microscopy demonstrated that the majority of particles are approx. 90 A diameter and present at a density of 780 +/- 190 micrometers-2 (+/- S.D.). If it is assumed that some of these particles represent the (Na+ + K+)-ATPase, the finding that they are largely confined to the convex fracture face suggests a predominant right-side-out orientation of these sarcolemmal vesicles that is consistent with biochemical assays. The sarcolemmal membrane width measured by electron microscopy (unhydrated membrane width of 50-70 A) is consistent with the unit cell dimensions of 56-77 A determined by lamellar X-ray diffraction (hydrated membrane width). A unit cell dimension of 56-62 A was also found by X-ray diffraction for sarcolemmal lipids extracted from these preparations, indicating that the isolated sarcolemmal preparations do not contain a significant surface coat (glycocalyx). As both cardiac and skeletal sarcoplasmic reticulum membranes have a 80-100 A membrane width, these findings demonstrate that the purified sarcolemmal membrane is structurally distinct from both cardiac and skeletal sarcoplasmic reticulum. In contrast to the protein-rich skeletal sarcoplasmic reticulum membrane, which contains a single essential protein responsible for the regulation of cytosolic Ca2+ concentration, the sarcolemma is a lipid-rich membrane that contains a variety of proteins associated with many regulatory functions served by this membrane in cardiac muscle.
通过对琼斯等人（琼斯 L.R.、马德洛克 S.W. 和贝施 H.R.（1980 年）《生物化学杂志》255 卷，9971 - 9980 页）的方法进行改进（科尔文 R.A.、阿沙瓦伊德 T.F. 和赫贝特 L.G.（1985 年）《生物化学与生物物理学报》812 卷，601 - 608 页）制备的高度纯化的犬心肌肌膜囊泡，其形态学和超微结构特性通过多种技术进行了检测。超薄切片电子显微镜显示主要是完整的单层囊泡，在脂质双层边界之外几乎没有染色。冷冻断裂电子显微镜表明，大多数颗粒直径约为 90 Å，密度为 780 ± 190 微米⁻²（±标准差）。如果假设这些颗粒中的一些代表（Na⁺ + K⁺）-ATP 酶，那么它们主要局限于凸面断裂面这一发现表明这些肌膜囊泡主要呈外翻取向，这与生化分析结果一致。通过电子显微镜测量的肌膜宽度（未水化膜宽度为 50 - 70 Å）与通过层状 X 射线衍射确定的晶胞尺寸（水化膜宽度）56 - 77 Å 一致。从这些制剂中提取的肌膜脂质通过 X 射线衍射也发现晶胞尺寸为 56 - 62 Å，表明分离的肌膜制剂不含有显著的表面涂层（糖萼）。由于心肌和骨骼肌肌质网膜的膜宽度为 80 - 100 Å，这些发现表明纯化的肌膜在结构上与心肌和骨骼肌肌质网不同。与富含蛋白质的骨骼肌肌质网膜不同，后者含有一种负责调节胞质 Ca²⁺浓度的单一必需蛋白质，肌膜是富含脂质的膜，含有多种与该膜在心肌中发挥的许多调节功能相关的蛋白质。
