The molecular mechanisms of membrane transport and the maintenance of compartmental diversity
GFP-FUSION PROTEINS HAVE REVOLUTIONIZED THE STUDY OF INTRACELLULAR TRANSPORT
There are various types of coated vesicles Each type is used for different transport steps in the cell. Mediate transport from Golgi & from plasma membrane Mediate transport from ER & Golgi
The assembly of a clathrin coat drives vesicle formation
Major coat protein: clathrin & adaptin There are at least four types of adaptins, each specific for a different set of cargo receptor. by charperone (hsp70)
Both the pinching-off and uncoating of coated vesicles are regulated processes
Not all transport vesicles are spherical Various size & shape
Monomeric GTPase control coat assembly
SNARE proteins and targeting GTPases guide membrane transport
Interacting SNAREs need to be pried apart before they can function again cytosol Cycle
Rab proteins (monomeric GTPase) help ensure the specificity of vesicle docking
Rab facilitate docking of transport vescicles. cycle Rab &its effector Structure vary greatly Function common (1.concentrate & tether vesicle near target site 2. Trigger release of SNARP control protein)
SNARE may mediate membrane fusion Process for SNARE concentrate in membrane fusion
Viral fusion proteins and SNAREs may use similar strategies
Transport from the ER through the golgi apparatus
Cargo Recruitment ER exit site 50nm vesicle > 200 mem protein
Only proteins that are properly folded and assembled can leave the ER ER resident protein Incomplete
CF (Cystic fibrosis) Defect in Cl- transport This is not because the mutation inactivated the protein, But because the active protein is discarded before it reaches the plasma membrane.
Transport from the ER to the Golgi apparatus is mediated by vesicular tubular clusters. Heterotypic fusion Homotypic memb fusion is not restricted to form VTC.
The structure formed when ER-derived vesicles fuse with one another are called.
ER retrival signal
The retrieval pathway to the ER uses sorting signals Lys-Asp-Glu-Leu (KDEL) KKXX at c-terminal end direct interact with COPI coat Short retrieval signal at c-terminal Resident ER membrane protein
Many proteins are selectively retained in the compartments in which they function Aggregation of proteins that function in the same compartment - called kin recognition
The golgi apparatus consists of an ordered series of compartments.
Two major classes of N-linked oligosaccharide complex High mannose No new sugar added in Golgi
Oligosaccharide processing in ER and Golgi
High specific endoglycosidase Can distinguish between these two type
Proteoglycans are assembled in the Golgi Apparatus O-linked glycosylation Proteoglycans are secreted or anchored to plasma membrane
What is the purpose of N- glycosylation? 1. N-linked is prevalent in all eukaryotes, but absent in procaryotes. 2. limited flexibility. 3. Recognition 4. Regulation of development 5. Protective coat unit 6. Cell-cell adhesion
The golgi cisternae are organized as a series of processing compartments
Matrix proteins form a dynamic scaffold that helps organize the apparatus
Transport from trans golgi network to lysosomes
Lysosome are the principal sites of intracellular digestion
Lysosomes are heterogeneous (morphology) The diversity reflects the wide range of digestive function.
Plant and fungal vacuoles are remarkably verstile lysosomes
M6P receptor recognizes lysosomal proteins in the Trans Golgi network (TGN)
The M6P receptor shuttles between specific membranes
Transport into the cell from the plasma membrane: endocytosis
Transport from the trans golgi network to the cell exterior: exocytosis
Chapter 13 practice 1.The endocytic and biosynthetic-secretory and retrieval pathway. 2.Utilization of different coats in vesicular traffic. 3.The role of SNAREs and SNAREs-interacting proteins in vesicle transport. 4.The traffic role of COPI &COPII coat shuttling between Golgi and ER. 5.What is KDEL signal and its role in retrieval pathway. 6.How to distinguish between the high-mannose oligosaccharide and complex oligosaccharide. 7.Write the full name for Glc NAc, NANA(sialic acid). 8.The functional compartmentization of Golgi apparatus. 9.Three pathways to degradation in lysosomes. 10.How to transport lysosomal enzyme to lysosome from ER. 11.Possible fates for endocytosed transmembrane receptor proteins. 12.The receptor-mediated endocytosis of LDL. 13.Three best-understanding pathways of protein sorting in trans Golgi.