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1、第五章 内膜系统,2019/7/10,2,Intracellular compartment and transport,5.1 引言(Introduction) 5.2 内质网（The Endoplasmic Reticulum） 5.3 高尔基体（Golgi complex ） 5.4 溶酶体（Lysosomes） 5.5 分泌和内吞（Secretory and Endocytosis ） 5.6 膜泡运输机制（The Mechanism of Vesicular Transport）,2019/7/10,3,5.1 Intruction Organelles and their func
2、tions,2019/7/10,4,The main functions of the membrane-enclosed compartments of a eukaryotic cell,Compartment Main function Cytosol Contains many metabolic pathways, protein synthesis Nucleus Contains main genome; DNA and RNA synthesis ER Synthesis of most lipids, synthesis of proteins for distributio
3、n to many organelles and to the plasma membrane Golgi apparatus Modification, sorting, and packaging of proteins and lipids for either secretion or delivery to another organelle Lysosomes Intracellular degradation Endosomes Sorting of endocytosed material Mitochondria ATP synthesis by oxidative phos
4、phorylation Chloroplasts ATP synthesis and carbon fixation by photosynthesis Peroxisomes Oxidation of toxic molecules,2019/7/10,5,Endomembrane System,2019/7/10,6,膜泡运输,2019/7/10,7,微粒体的纯化过程,?,2019/7/10,8,Three mechanisms that proteins are imported into organelles,2019/7/10,9,Some typical protein sorti
5、ng signals,2019/7/10,10,2019/7/10,11,ER is a network of membrane-enclosed tubules and sacs (cisternae) that extends from the nuclear membrane throughout the cytoplasm. ER is the largest organelle of most eukaryotic cells. Its membrane may account for about half of all cell membranes. the space enclo
6、sed by the ER may represent about 10% of the total cell volume.,5.2 Endoplasmic reticulum(ER),2019/7/10,12,Endoplasmic reticulum,2019/7/10,13,Rough endoplasmic reticulum (RER) Smooth endoplasmic reticulum (SER) 内质网的外表面称为胞质溶胶面 (sytosolic space) 内表面称为潴泡面(cisternal space) 特殊类型的内质网 微粒体(microsome) 肌质网(sa
7、rcoplasmic reticulum),2019/7/10,14,糖原分解与游离葡萄糖释放 脂类的合成与转运 解毒作用:药物脱毒与相关的氧化酶 Ca2+离子浓度的调节作用,Function of sER,2019/7/10,15,糖原分解与游离葡萄糖释放,磷脂酰胆碱的合成过程,2019/7/10,16,2019/7/10,17,2019/7/10,18,磷脂转运的三种方式,2019/7/10,19,解毒作用 光面内质网含有丰富的氧化酶系统(如细胞色素P450、NADH细胞色素C还原酶等)能使许多有害物质解毒,转化为易于排出的物质。 混合功能的氧化酶(mixed-function oxida
8、se) 每分子的底物被氧化需要消耗一分子氧,并且将NADPH转变成NADP+ 该氧化过程消耗的氧分子中有一个氧原子出现在水中，另一个氧原子出现在产物中 故此将催化该反应的酶称为混合功能的氧化酶。,2019/7/10,20,光面内质网的氧化作用,2019/7/10,21,粗面内质网的功能 -信号肽与蛋白质运输,2019/7/10,22,信号肽(Signal peptide) 的特性,序列特征 15-35个氨基酸残基，其中含有4-12个疏水残基 位置: N-端突出的一段肽 内含信号肽。,2019/7/10,23,体外实验证明SRP颗粒、SRP受体的作用,2019/7/10,24,信号假说(sign
9、al hypothesis),1975年，Blobel等正式提出了信号假说,要点是: 合成始于游离核糖体; N端信号序列靠自由碰撞与内质网膜接触,然后插入内质网的膜; 蛋白质以袢环形式穿过内质网的膜; 蛋白的存在方式: 若信号序列被信号肽酶切除:完全进入腔 若是停止转移信号: 膜蛋白,2019/7/10,25,信号识别颗粒与停靠蛋白,signal recognition partical, SRP SRP is a cytosolic ribonucleoprotein particle Six discrete polypeptides A 300-nucleotide RNA 三个功能域:
10、 翻译暂停结构域(P9/P14) 信号肽识别结合位点(P54) SRP受体蛋白结合位点(P68/P72)。,2019/7/10,26,SRP蛋白的晶体结构,2019/7/10,27, SRP受体（SPR receptor） 是SRP在内质网膜上的受体蛋白 两个亚基:亲水的亚基, 疏水的亚基 转位因子（translocator） 4 copies of the Sec61 complex assemble to form a cylinder translocon channel 56 nm high and 8.5 nm in diameter, with a central pore, ro
11、ughly 2 nm in diameter 哺乳动物细胞中有三种类型的Sec61, 即、和,Figure 12-42 Molecular Biology of the Cell ( Garland Science 2008),转位因子复合物,Figure 12-43 Molecular Biology of the Cell ( Garland Science 2008),转位因子复合物,Figure 12-44 Molecular Biology of the Cell ( Garland Science 2008),2019/7/10,31,蛋白质转移到内质网上合成的过程,Figure
12、12-45 Molecular Biology of the Cell ( Garland Science 2008),2019/7/10,33,跨膜信号与膜蛋白的定向,单次跨膜蛋白 起始转移信号(start transfer signal) 终止转移序列(stop transfer sequence) 可切割的信号序列(Cleavable signal sequence) (N-端) 内部信号序列(internal signal sequence) (internal noncleavable signal sequences ),Figure 12-46 Molecular Biology
13、 of the Cell ( Garland Science 2008),Figure 12-47 Molecular Biology of the Cell ( Garland Science 2008),Figure 12-48 Molecular Biology of the Cell ( Garland Science 2008),Figure 12-49 Molecular Biology of the Cell ( Garland Science 2008),Figure 12-58 Molecular Biology of the Cell ( Garland Science 2
14、008),2019/7/10,39,蛋白质在内质网中的加工与修饰,The formation of disulfide bonds between the side chains of cysteine residues:protein disulfide isomerase(PDI) N-linked glycosylation(Asn-X-Ser/Thr) Addition of glycosylphosphatidylinositol (GPI,糖基磷脂酰肌醇) anchors Export of Proteins from the ER,2019/7/10,40,The formati
15、on of disulfide bonds,2019/7/10,41,N-linked glycosylation,2019/7/10,42,Figure 12-51 Molecular Biology of the Cell ( Garland Science 2008),2019/7/10,44,N-连接糖基化在ER蛋白质折叠的质控中所起的作用,Figure 12-54 Molecular Biology of the Cell ( Garland Science 2008),Figure 12-55a Molecular Biology of the Cell ( Garland Sci
16、ence 2008),Figure 12-55b Molecular Biology of the Cell ( Garland Science 2008),Figure 12-56 Molecular Biology of the Cell ( Garland Science 2008),Addition of GPI anchors,2019/7/10,49,Export of Proteins from the ER,2019/7/10,50,5.3 Golgi apparatus,高尔基器(Golgi apparatus)或高尔基复合体(Golgi complex),意大利科学家Camillo Golgi在 1898年发现的。 4-8 flattened membrane vesicles or sacs surrounded by a number of spherical m
