What We Learnt in Our Last Class
Compartmentalization in Eukaryotic Cells and study approaches sER function Synthesis of steroid hormones Detoxification Glucose 6-phosphatase Sequestering calcium rER Synthesis of secretory proteins - signal hypothesis (component and functions) Synthesis of integral membrane proteins Membrane biosynthesis in the ER Glycosylation and quality control of the ER
Figure 13-3a Molecular Biology of the Cell (© Garland Science 2008)
Why all the trouble? What is the purpose of glyosylation?
糖基化的功能
• Oligosaccharide protrudes from protein surface, preventing
other proteins from approaching, thereby making the protein resistant to digestion.蛋白更稳定，不易降解 • N-linked glycoslylation promotes protein folding in two ways: 促进蛋白折叠
Figure 13-26a Molecular Biology of the Cell (© Garland Science 2008)
Immunofluorescence of Golgi-GFP in a plant cell
Figure 13-26b Molecular Biology of the Cell (© Garland Science 2008)
Class II
4 高尔基体The Golgi complex 5 膜泡运输Types of vesicle transport and membrane fusion
4. The Golgi Complex
4.1 The Golgi Apparatus Consists of an Ordered Series of Compartments. 结构：主体为4-8排列较整齐的扁平膜囊 4.2 Glycosylation in the Golgi complex 功能1：糖基化 4.3 The movement of materials through the Golgi complex
The vesicular transport and the cisternal maturation models are not mutually exclusive. Evidence suggests that transport may occur by a combination of the two mechanisms:
The Golgi Apparatus
Cisternae: flattened, membrane-enclosed compartments; diameter 0.5-1.0 μm, arranged in an orderly stack. the cis face (or entry face) is close to the ER the trans face (or exit face) Both faces are closely associated with a network of interconnected tubular and cisternal structures: Figure 13-25a Molecular Biology of the Cell (©(CGN) Garland Science 2008) the cis Golgi network and the trans Golgi network (TGN)
功能2：物质运输
EM of an Animal Cell Golgi
Figure 13-25b Molecular Biology of the Cell (© Garland Science 2008)
EM of a Plant Cell Golgi
Chlamydomonas
Figure 13-25c Molecular Biology of the Cell (© Garland Science 2008)
高尔基体
结构特点
• 主体为4-8排列较整齐的扁平膜囊（多弓形, 中 间囊腔较窄; 周缘多泡状）堆叠在一起，周围又有大 量大小不等的囊泡。
极性细胞器: 在细胞中有比较恒定的位置和方向; 物
质从一侧进入，另一侧输出。 顺面(cis face)/形成面(forming face)—靠近细胞 核的一面，凸面 反面(trans face)/成熟面(mature face)—面向细 胞膜的一侧，凹面
1. it has a direct role in making folding intermediates more soluble thereby preventing their aggregation. 2. the sequential modifications of the N-linked oligosaccharide establish a “glyco-code” that marks the progression of protein folding and mediates the binding of the protein to chaperones and lectins. •
Oligosaccharide processing in Golgi Compartments
Figure 13-28 Molecular Biology of the Cell (© Garland Science 2008)
（2）Golgi Complex as a “Processing Plant” 物质运输的枢纽
Chapter 8: Intracellular Compartments & Protein sorting (分选）
Class I
1. The endomembrane systems of eukaryotic cells 2. Experimental approaches 3 The ER and its function
•The Golgi complex contains fewer than eight cisternae. •CGN: Function as a sorting station that distinguishes between proteins back to the ER vs. those that will proceed to the next Golgi. •TGN: Function as a sorting station that distinguishes vesicles to the plasma membrane or to other intracellular destinations.
vesicles carry cargos in an anterograde direction, cisternae remains stable.
cisternae progress from cis to trans, vesicles travel in a retrograde direction
The Golgi complex plays a key role in the assembly of glycoproteins and glycolipids.
The core carbohydrate of N-linked oligosaccharides（N-连接的 糖基化） is assembled in the rER. Modifications to N-linked oligosaccharides are completed in the Golgi complex. O-linked oligosaccharides （O-连接的糖基化,Ser/Try/Lys-O-H） takes place in Golgi complex.
5. Intracellular Vesicular Traffic
•Three types of vesicles:
5.1 COPII- coated vesicles (ER to Golgi) 5.2 COPI - coated vesicles (back to ER) 5.3 Clathrin - coated vesicles (from TGN to endosome, lysosome, plant vacuoles) 5.4 Fusion between vesicles and target membranes
5 膜泡运输和膜融合（p82）
Vesicle budding, traffiking and fusion
Vesicle budding
Vesicle trafficking
membrane fusion and exocytosis
Vesicle budding
[From K. Matsuoka et al., 1988, Cell 93(2):263.]
高尔基体功能
4.2 Glycosylation in the Golgi complex 功能1：糖基化