southeast university genetic center 第四节 细胞质的结构与功能 ( 一 ) The Structure and Function of Cell Cytoplasm

一. 细胞内膜系统概述 Endomembrane System in Eukaryotic Cells 二. 膜性细胞器的结构及相关性 The structural and functional relationship between the membrane-enclosed organelles. 三. 细胞内蛋白质分选机制 The mechanism of Protein Sorting 四. 蛋白质合成后修饰 The ways of protein modifications after they are synthesized

一. 细胞内膜系统概述 Endomembrane System in Eukaryotic Cells  Endomembrane System : The structural and functional relationship organelles with the membrane enclosed, including ER, Golgi complex, lysosome, endosomes, secretory vesicles.

Compartmentalization in Eukaryotic Cells

The Compartmentalization in Eukaryotic Cells

1. 膜性细胞器 – 内质网 (endoplasmic reticulum) – 高尔基复合体 (golgi complex) – 溶酶体 (lysosome) – 过氧化物酶体 (peroxisome) – 线粒体 (mitochondria) 2. 非膜相结构 – 核糖体 (ribosome) – 细胞骨架 (cytoskeleton) 细胞器 (organelles)

内质网 内质网（ Endoplasmic reticulum, ER ）

粗面内质网 (RER) 滑面内质网 (SER) RER has ribosomes on the cytosolic side of continuous, flattened sacs (cisternae) SER is an interconnecting network of tubular membrane elements.

粗面内质网的功能 Functions of the RER 1. Proteins synthesized on ribosomes of RER 分泌蛋白 (secretory proteins) 膜内在蛋白 (integral membrane proteins) 细胞器可溶性蛋白 (soluble proteins of organelles)

2. Modification and processing of newly synthesized proteins: glycosylation in the RER

N-linked(N- 连接 ): linked to the amide nitrogen of asparagine (ER) O-linked(O- 连接 ): linked to the hydroxyl group serine or threonine via GalNac (Golgi) 糖蛋白的类型 The class of glycoproteins

3. Synthesis of membrane lipids Most membrane lipids are synthesized entirely in the ER. There are two exceptions: sphingomyelin and glycolipids, (begins in ER; completed in Golgi); some of the unique lipids of the Mit and Chl membranes.

Synthesis of steroids in endocrine cells. Detoxification of organic compounds in liver cells. System of oxygenases---cytochrome p450 family Sequestration of Ca2+. 滑面内质网的功能 Functions of the SER

高尔基体 (Golgi complex, GC)

高尔基体的功能 The functions of GC 1. Glycosylation in the Golgi complex

2.The processing and sorting stations where proteins are modified, segregated and then shipped in different directions.

3. Vesicular transport within the Golgi apparatus

溶酶体 (Lysosome) 初级溶酶体 Primary lysosomes 次级溶酶体 Second lysosomes heterophagic autophagic 残余小体 Residual body

溶酶体的特性 Characteristics of Lysosomes 1. Lysosome is a heterogenous organelle 2. Plenty of acid hydrolases (Acid phosphatase is marker enzyme) 3. Lysosome membrane H+-pumps: internal proton concentration is kept high by H+-ATPase Glycosylated proteins: protect the lysosome from self-digestion. Transport proteins: transporting digested materials.

溶酶体的功能 ---- 细胞消化与防御 The Functions of Lysosomes 自噬作用 autophagy 异噬作用 phagocytosis

Lysosomes in phagocytosis and autophagy

溶酶体的发生 Biogenesis of Lysosomes The transport of newly synthesized lysosomal hydrolases to lysosomes

Mannose 6-phosphate residues target proteins to lysosomes

过氧化物酶体（ peroxisome ）

细胞内蛋白质分选机制 细胞内蛋白质分选机制 The mechanism of Protein Sorting Proteins are imported into organelles by three mechanisms: Gated Transport: Transport through nuclear pores Transmembrane transport: ER, Mit, Chl, Per Vesicular transport: ER-Golgi-PM-Lys

蛋白分选 (Protein Sorting)

Some Typical Signal Sequence

Two ways that a sorting signal can be built into a protein Signal peptides ( 信号肽 ) Signal patches ( 信号斑 )

The signal sequence of growth hormone Most signal sequences contain a stretch of hydrophobic amino acids, preceded by basic residues (e.g., Arginine)

跨膜运输 (Transmembrane transport)

Action of chaperones during protein transport 分子伴侣在蛋白转运中的作用

Import of proteins into mitochondria 蛋白到线粒体的跨膜 运输

Vesicular transport 囊泡运输

Gated Transport 孔门运输 Nuclear Pore Complex Molecule Transport

. 核定位信号 Nuclear localization signals The T antigen nuclear localization signal is a single stretch of amino acids. The nuclear localization signal of nucleoplasmin is bipartite, consisting of a Lys-Arg sequence, followed by a Lys-Lys-Lys-Lys sequence located ten amino acids farther downstream

Protein glycosylation in the ER 蛋白质合成后修饰 蛋白质合成后修饰 The ways of protein modifications after they are synthesized

(N-link) Protein glycosylation in the ER (N-link)

N- 连接的糖基化蛋白在高尔基体中进一步加工 Processing of N-linked oligosaccharides in the Golgi

Proteolytic processing of insulin 胰岛素合成后的加工过程