STRUCTURE AND FUNCTION OF THE NUCLEAR PORE COMPLEX

核孔复合体(NPC)是一个1200-1400的大集合体 直径为埃，厚600-800埃，横跨 核包膜。全国人大是两国人民之间的沟通渠道 细胞核和细胞质，允许小分子的被动扩散 分子和离子，并积极运输大分子和 核糖核蛋白颗粒在这两个隔间之间。腺瘤 疱疹病毒在将DNA释放到鼻咽癌之前与鼻咽癌结合 原子核。完整的逆转录病毒衣壳通过 全国人大。尽管全国人大在牢房中的显著位置和它的 控制(例如)核质交换的重要性荷尔蒙 受体复合体、调节蛋白、mRNPs、核糖体和病毒 组件，对此组件知之甚少： 不能分离出足够数量的鼻咽癌来进行生化 用x射线方法进行表征或分析，只有很低的 分辨率3-D信息关于它的结构变化很少 已鉴定出(&lt；10%)NPC蛋白及其分子机制 运输过程中的一部分是未知的。 这项工作的长期目标是了解 鼻咽癌的高分辨率及其分子机制的研究 主动的核质运输。完成的任务 这里描述的工作将代表着在实现 这些目标。 冷冻电子显微镜与计算机图像处理相结合将 用于确定投影地图和三维地图 由改进的制备方法得到的分辨率约为50埃 洗涤剂释放的NPC。随后，数字的3-D位置 重要的鼻咽癌蛋白--包括核必需的那些 运输-将通过免疫电子显微镜和 图像分析。冷冻干燥金属阴影的检验 人工涂布核膜的准备工作将揭示 在核侧和细胞质侧的结构差异 全国人大。这些发现将与3D地图中的细节相关。 使用人工合成的核定位信号肽的实验已经 被设计来调查中央插头的身份 NPC，并可提供有关运输的结构信息 仪器。

The nuclear pore complex (NPC) is a large assembly 1200-1400 angstroms in diameter and 600-800 angstroms thick which spans the nuclear envelope. The NPC is the communication pathway between the nucleus and the cytoplasm, allowing the passive diffusion of small molecules and ions and actively transporting large macromolecules and ribonucleoprotein particles between these two compartments. Adeno and herpes viruses bind to the NPC prior to release of their DNA into the nucleus. Intact retrovirus capsids are transported through the NPC. Despite the NPC's prominent location in the cell and its importance in controlling nucleoplasmic exchange of (e.g.) hormone receptor complexes, regulatory proteins, mRNPs, ribosomes and virus components, there is relatively little known about this assembly: the NPC cannot be isolated in sufficient quantities for biochemical characterization or analysis by x-ray methods, only very low resolution 3-D information is available on its structure vary few (<10%) NPC proteins have been identified and the molecular mechanisms of the transport processes are unknown. The long term goals of the work are to understand the structure of the NPC ar high resolution and to elucidate the molecular mechanism of active nucleocytoplasmic transport. The accomplishment of the work described herein will represent major progress towards attaining these goals. Cryo-electron microscopy coupled with computer image processing will be used to determine projection maps and a 3-dimensional map at a resolution of about 50 Angstroms from improved preparations of detergent-released NPCs. Subsequently, the 3-D location of a number of important NPC proteins-- including those necessary for nuclear transport -- will be determined by immunoelectron microscopy and image analysis. An examination of freeze-dried, metal-shadowed preparations of manually spread nuclear envelopes will reveal structural differences on the nuclear and cytoplasmic sides of the NPC. These findings will be related to details in the 3-D map. Experiments using synthetic nuclear localization signal peptides have been designed to investigate the identity of the central plug of the NPC and may provide structural information on the transport apparatus.