Napolitano C A, Cooke P, Segalman K, Herbette L
Biophys J. 1983 May;42(2):119-25. doi: 10.1016/S0006-3495(83)84377-X.
The arrangement of the calcium pump protein in the isolated sarcoplasmic reticulum (SR) membrane was examined by optical diffraction of freeze-fracture electron micrographs. Several states of protein particle organization were observed: random, hexagonal and tetragonal packing, and a mixture of hexagonal and tetragonal packing. This suggests that the time-averaged positions of protein particles in the plane of the SR membrane are weakly defined. In addition, there appears to be a greater degree of local or short-range order compared to long-range order within the field of freeze-fracture particles. We utilized measurements from tetragonally or hexagonally packed arrays to determine a unit cell area occupied by each freeze-fracture particle and its associated lipid matrix. When these unit cell areas and the stereologically determined area per freeze-fracture particle were compared to the cross-sectional area occupied by a single calcium pump protein and its associated lipid, obtained by x-ray and neutron diffraction methods, we concluded that each freeze-fracture particle probably represents a dimer of pump protein molecules in the plane of the SR membrane.
通过冷冻蚀刻电子显微照片的光学衍射，研究了分离的肌浆网（SR）膜中钙泵蛋白的排列。观察到蛋白质颗粒组织的几种状态：随机排列、六边形和四边形排列，以及六边形和四边形排列的混合。这表明SR膜平面中蛋白质颗粒的时间平均位置定义不明确。此外，与冷冻蚀刻颗粒领域内的长程有序相比，似乎存在更大程度的局部或短程有序。我们利用来自四边形或六边形排列阵列的测量数据，确定每个冷冻蚀刻颗粒及其相关脂质基质所占据的单位晶胞面积。当将这些单位晶胞面积和通过体视学确定的每个冷冻蚀刻颗粒的面积，与通过X射线和中子衍射方法获得的单个钙泵蛋白及其相关脂质所占据的横截面积进行比较时，我们得出结论，每个冷冻蚀刻颗粒可能代表SR膜平面中泵蛋白分子的二聚体。
