MACROMOLECULAR STRUCTURE

纯化的包被囊泡的结构和组成异质性 从大鼠肝脏中的LCV的质量分布进行了研究， 以及通过用非离子萃取从它们中得到的颗粒 洗涤剂Triton X-100，并通过除去它们的网格蛋白涂层， 控制pH和离子强度。 单个粒子的质量 通过暗场扫描的计算机图像处理， 未染色冻干制剂的透射电子显微照片; 这些数据被汇编成统计分布， 然后将数据与全球的生物化学测定相关联， 蛋白质、磷脂和胆固醇的含量 准备工作 我们发现，大约30%的"LCV"实际上不包含 膜囊泡（在脑包被囊泡的情况下大于70%）， 但具有蛋白质核心。 剩下的70%含有囊泡， 根据材料的相对量区分的两种类型的 包含在它们的管腔中。 含有囊泡的LCV明显 异质的，质量在四倍范围内变化（约50至200 兆道尔顿-MDa）和两倍直径范围（约80至160 nm）。 的 这种颗粒的平均质量为80 MDa，其中46 MDa由以下物质贡献： 网格蛋白和其他外壳蛋白，10 - 12 MDa磷脂和 胆固醇和20 - 22 MDa的囊泡蛋白。 根据SDS-PAGE估计 后者构成了极其多样化的蛋白质集合， 除了一个相对突出的双峰外， 46kDa。 此外，基于各种电子的结构分析 通过数字图像处理增强的显微镜方法已经被 在许多其他生物系统上进行，包括角蛋白 中间丝，脊椎动物骨骼的肌丝网格 肌肉、百日咳杆菌菌毛和 噬菌体T7。

The structural and compositional heterogeneity of coated vesicles purified from rat liver has been investigated by compiling mass distributions of LCV and of particles derived from them both by extraction with the non-ionic detergent Triton X-100 and by removal of their clathrin coats by manipulation of pH and ionic strength. The masses of individual particles were determined by computer image processing of dark-field scanning transmission electron micrographs of unstained frozen-dried preparations; these data were compiled into statistical distributions and the resulting data were then correlated with biochemical determinations of the global contents of protein, phospholipid, and cholesterol in the respective preparations. We found that about 30% of "LCV" do not, in fact, contain membrane vesicles (greater than 70% in the case of brain coated vesicles), but have proteinaceous cores. The remaining 70% contain vesicles seemingly of two kinds differentiated according to the relative amounts of material contained within their lumens. Vesicle-containing LCV are markedly heterogeneous, with masses varying over a four-fold range (about 50 to 200 megadaltons-MDa) and a two-fold diameter range (about 80 to 160 nm). The average mass of such particles is 80 MDa, of which 46 MDa is contributed by clathrin and other coat proteins, 10-12 MDa by phospholipid and cholesterol, and 20-22 MDa by vesicle proteins. As estimated by SDS-PAGE the latter constitute an extremely diverse collection of proteins that are present in vary samll amounts, except for a relatively prominent doublet of 46kDa. In addition, structural analyses based on various electron microscopical methods reinforced by digital image processing have been performed on a number of other biological systems, including keratin intermediate filaments, the myofilament lattice of vertebrate skeletal muscle, the fimriae of Bordetella pertussis, and the tail-fibers of bacteriophage T7.