Chapter 25 Protein trafficking 莘大
Chapter 25 Protein trafficking
25.1 Introduction 25.2 Oligosaccharides are added to proteins in the er and golgi 25.3 The Golgi stacks are polarized 25.4 Coated vesicles transport both exported and imported proteins 25.5 Different types of coated vesicles exist in each pathway 25.6 Cisternal progression occurs more slowly than vesicle movement 25.7 Vesicles can bud and fuse with membranes 25.8 SNARES control targeting 25.9 The synapse is a model system for exocytosis 25.10 Protein localization depends on specific signals 25 11 ER proteins are retrieved from the golgi 25. 12 Brefeldin A reveals retrograde transport 25. 13 Receptors recycle via endocytosis 25. 14 Internalization signals are short and contain tyrosine 消当
25.1 Introduction 25.2 Oligosaccharides are added to proteins in the ER and Golgi 25.3 The Golgi stacks are polarized 25.4 Coated vesicles transport both exported and imported proteins 25.5 Different types of coated vesicles exist in each pathway 25.6 Cisternal progression occurs more slowly than vesicle movement 25.7 Vesicles can bud and fuse with membranes 25.8 SNAREs control targeting 25.9 The synapse is a model system for exocytosis 25.10 Protein localization depends on specific signals 25.11 ER proteins are retrieved from the Golgi 25.12 Brefeldin A reveals retrograde transport 25.13 Receptors recycle via endocytosis 25.14 Internalization signals are short and contain tyrosine
25.1Introduction Sorting signal is a motif in a protein (either a short sequence of amino acids or a covalent modification) that is required for it to be incorporated into vesicles that carry it to a specific destination 消当
Sorting signal is a motif in a protein (either a short sequence of amino acids or a covalent modification) that is required for it to be incorporated into vesicles that carry it to a specific destination. 25.1 Introduction
25.1Introduction Figure 25.1 Proteins that enter the endoplasmic reticulum are Secreted proteins membrane transported to the golgi and towards the plasma membrane Gotai transact prote ins to plasma membrane Specific signals cause proteins trans Golgi t to be returned from the golgi ns occur to the eR, to be retained in the rom ch fo tai ns bosom es Golgi, to be retained in the plasma membrane or to be ransport to golgi prot eins retum to transported to endosomes and Proteins enter E uring synthesi transported between the plasma/oawvrg oiyrcosyation lysosomes. Proteins may be Endoplasmic reticulum385> membrane and endosomes 消当
Figure 25.1 Proteins that enter the endoplasmic reticulum are transported to the Golgi and towards the plasma membrane. Specific signals cause proteins to be returned from the Golgi to the ER, to be retained in the Golgi, to be retained in the plasma membrane, or to be transported to endosomes and lysosomes. Proteins may be transported between the plasma membrane and endosomes. 25.1 Introduction
25.1Introduction Vesicle fusion CYTOSOL Figure 25.2 Vesicles are onor com partment sicle contacts released when they bud from CYTOSoL' target membrane a donor compartment and are surrounded by coat proteins(left). During fusion, Coat is rem oved the coated vesicle binds to a Vesda buds from mem brane target compartment, IS SV2 Vesicle fuses with uncoated. and fuses with the target mem brane target membrane, releasing Veside is released its contents(right) 消当
Figure 25.2 Vesicles are released when they bud from a donor compartment and are surrounded by coat proteins (left). During fusion, the coated vesicle binds to a target compartment, is uncoated, and fuses with the target membrane, releasing its contents (right). 25.1 Introduction
○ N-acety-gu 25.2 Oligosaccharides ● Mannose● Glucose are added to proteins in Dolich the er and golgi Glycosyl transferase ENDOPLASMIC RETICULUM Figure 25.3 An oligosaccharide is formed on dolichol and Ho- CHo-CANt Asparagine in target c=o: t transferred by glycosyl transferase to asparagine of a target protein = 消当 Glycoprotein
Figure 25.3 An oligosaccharide is formed on dolichol and transferred by glycosyl transferase to asparagine of a target protein. 25.2 Oligosaccharides are added to proteins in the ER and Golgi
○N-acet/ glucosamine ● Mannose● Glucose 25.2 Oligosaccharides are added to proteins in the ER and golgi ●●鲁 Figure 25.4 Sugars are R glucosidases|&‖ removed in the er in a fixed NH order, initially comprising 3 H HC-CH2○鲁● glucose and 1-4 mannose residues. This trimming ↓ ER mannosidase generates a high mannose oligosaccharide. High mannose c2c○○ oligosaccharide 消当
Figure 25.4 Sugars are removed in the ER in a fixed order, initially comprising 3 glucose and 1-4 mannose residues. This trimming generates a high mannose oligosaccharide. 25.2 Oligosaccharides are added to proteins in the ER and Golgi
Golgi mannosidase 25.2 Oligosaccharides are added to proteins in the er and Golgi ↓ N-acetyl- glucosamine transfe rase Figure 25.5 Processing for a complex oligosaccharide occurs in the Golgi and trims the original preformed unit to the ↓ Golgi manno sida se‖ inner core consisting of 2 N-acetyl glucosamine and 3 mannose residues HC H resistance Then further sugars can be added, in the order in which the transfer enzymes are Golgi enzymes add further encountered to generate a terminal residues Galsialic acid region containing N-acetyl-glucosamine HC-CH galactose, and sialic acid winner core Terminal region 消当
Figure 25.5 Processing for a complex oligosaccharide occurs in the Golgi and trims the original preformed unit to the inner core consisting of 2 N-acetylglucosamine and 3 mannose residues. Then further sugars can be added, in the order in which the transfer enzymes are encountered, to generate a terminal region containing N-acetyl-glucosamine, galactose, and sialic acid. 25.2 Oligosaccharides are added to proteins in the ER and Golgi
25.2 Oligosaccharides are added to proteins in the er and golgi 含2 Figure 25. 6 The golgi apparatus consists of a series of individual membrane stacks Photograph kindl provide d by alain Rambourg 消当
Figure 25.6 The Golgi apparatus consists of a series of individual membrane stacks. Photograph kindly provided by Alain Rambourg. 25.2 Oligosaccharides are added to proteins in the ER and Golgi
25.2 Oligosaccharides are added to proteins in the er and golgi 句f mannose-6-P receptors sialyl transferase Figure 25. 7 A Golgi acid phosphatase stack consists of a series galacto sy tran sferase F rans cistern of cisternae organized with cis to trans polarity 1P-NAc-qlucosaminidase NADPase mediakeisterna Protein modifications mannosidase‖l occur in order as a gIcN-acetyl-transferase mannosidase I as cisterna protein moves from the Golgi: c isease cis face to the trans face 消当
Figure 25.7 A Golgi stack consists of a series of cisternae, organized with cis to trans polarity. Protein modifications occur in order as a protein moves from the cis face to the trans face. 25.2 Oligosaccharides are added to proteins in the ER and Golgi
