王金发细胞生物学第11章_(PPTminimizer).ppt

CHAPTER 11 Cell Nucleus and Chromosome 11.1 Nuclear Envelope 11.1.1 Structure of the Nuclear Envelope ?一般结构 ◆Outer nuclear membrane ◆Inner nuclear membrane ◆Perinuclear space 两层核膜之间的空隙, 宽15-30nm, 其中充满无定形物质 ◆核纤层(lamina) ?核孔 ◆由内外两层膜的局部融合而成 ◆核孔的直径为80-120nm。 ◆一个典型的哺乳动物的核膜上有3000-4000个核孔,相当于每平方微米的核膜上有10-60个。 ◆合成功能旺盛的细胞,核孔的数量较多。 11.1.2 Functions of the  Nuclear Envelope ◆基因表达的时空隔离 ◆核膜成为保护性屏障, 使核处于 一微环境 ◆染色体的定位和酶分子的支架 ◆物质运输 ?核孔复合体的结构:鱼笼模型 ◆胞质环(cytoplasmic ring) ◆细胞质颗粒(cytoplasmic granular) ◆核质环(nucleoplasmic ring) ◆中央运输蛋白 ◆辐条(spoke) ◆核被膜网格(Nuclear Envelope lattice) ◆笼状体(basket) ?核孔运输特点 ◆被动运输 ◆主动运输 ●信号引导 ●双向性 11.2.1核蛋白运输机制 ?基本概念 ◆核蛋白(nuclear protein) ◆核定位信号(nuclear localization signals ,NLS) ◆核输出信号(nuclear export signals, NES) ◆输入蛋白(importin) ◆输出蛋白(exportin) ?核蛋白的输入 ◆核质蛋白(nucleoplasmin)实验 ◆核蛋白输入机理 ●输入蛋白 ●Ran蛋白 ●RCC1 核蛋白输入机理 ?核内RNA与蛋白质输出 11.3 分子伴侣(chaperones) 11.3.1 分子伴侣的发现及种类 ◆The term “chaperone was first used by Ron Laskey and his colleagues to describe a protein (nucleoplasmin) that is required for the assembly of nucleosomes from histones and DNA. ◆Nucleoplasmin binds to histones and mediates their assembly into nucleosomes, but nucleoplasmin itself is not incorporated into the final nucleosome structure. ◆Chaperones thus act as catalysts that facilitate assembly without being part of the assembled complex. ?分子伴侣的概念及其特点 ◆1991年Ellis等人提出: ●由不相关类的蛋白质组成的一个家系 ●它们介导其它蛋白质的正确装配 ●但自己不成为最后功能结构中的组分。 ◆该概念有以下特点: ●凡具有“介导”功能的蛋白,都称为分子伴侣,可以是完全不同的蛋白质; ●作用机理尚不清楚,故用“介导”二字,伸缩性较大； ●分子伴侣一定不是最终结构的组成部分,但不一定是一个分离的实体; ●装配的涵意比较广,包括:帮助新生肽的折叠,越膜定位, 亚基组装等。 ◆It is important to note that : ● Chaperones do not convey additional information required for the folding of polypeptides into their correct three-dimensional conformations. ● The folded conformation of a protein is determined solely by its amino acid sequence. ● Rather, chaperones catalyze protein folding by assisting the self-assembly process. ●They appear to function by binding to and stabilizing unfolded or partiall