Meldolesi J, Jamieson J D, Palade G E
J Cell Biol. 1971 Apr;49(1):109-29. doi: 10.1083/jcb.49.1.109.
The subcellular components involved in the synthesis, transport, and discharge of secretory proteins in the guinea pig pancreatic exocrine cell have been isolated from gland homogenates by differential and gradient centrifugation. They include rough and smooth microsomes derived respectively from the rough endoplasmic reticulum and Golgi periphery, a zymogen granule fraction consisting mainly of mature zymogen granules and a smaller population of condensing vacuoles, and a plasmalemmal fraction. Membrane subfractions were obtained from the particulate components by treatment with mild (pH 7.8) alkaline buffers which extract the majority (>95%) of the content of secretory proteins, allowing the membranes to be recovered from the extracting fluid by centrifugation. The purity of the fractions was assessed by electron microscopy and by assaying marker enzymes for cross-contaminants. The rough and smooth microsomes were essentially free of mitochondrial contamination; the smooth microsomes contained <15% rough contaminants. The zymogen granule fraction and its derived membranes were free of rough microsomes and contained <3% contaminant mitochondria. The plasmalemmal fraction was heterogeneous as to origin (deriving from basal, lateral, and apical poles of the cell) and contained varying amounts of adherent fibrillar material arising from the basement membrane and terminal web. The lipid and enzymatic composition of the membrane fractions are described in the following reports.
通过差速离心和梯度离心从豚鼠胰腺外分泌细胞的腺体匀浆中分离出了参与分泌蛋白合成、运输和分泌的亚细胞成分。它们包括分别来源于糙面内质网和高尔基体周边的糙面和滑面微粒体、一个主要由成熟酶原颗粒和少量浓缩泡组成的酶原颗粒组分，以及一个质膜组分。通过用温和的（pH 7.8）碱性缓冲液处理颗粒成分获得膜亚组分，该缓冲液可提取大部分（>95%）分泌蛋白的内容物，从而通过离心从提取液中回收膜。通过电子显微镜和检测交叉污染物的标记酶来评估各组分的纯度。糙面和滑面微粒体基本没有线粒体污染；滑面微粒体含有<15%的糙面污染物。酶原颗粒组分及其衍生的膜没有糙面微粒体，并且含有<3%的污染线粒体。质膜组分在来源上是异质的（来源于细胞的基底、侧面和顶端极），并且含有不同量的来自基底膜和终末网的附着纤维状物质。膜组分的脂质和酶组成在以下报告中描述。
