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Lecture 8

Lecture 8 - Chapter 13 - January 31.docx

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York University
BIOL 2021
Patricia Lakin- Thomas

January 31, 2013 Lecture 7: Chapter 13 – Vesicle Transport Figure 12.6  Biosynthetic: secretory pathway o Includes new proteins, carbs, lipids  Delivered to plasma membrane or extracellular space  Endocytosis o PM romeced and delivered to endosomes  Retrieval Pathways (in blue) o Molecular return to be reused Transport Vesicles  Membrane enclosed container, travels between compartments  Cargo: anything carried by vesicles  Lumen of vesicles is topologically equivalent: o Does not have to go through a hole in the membrane, fuses instead)  Vesicle budding and fusion o Donor  budding  target fusion  Cargo stays in lumen or membrane  Proteins never cross membranes o PROBLEMS:  How do vesicles bud and fuse?  How is identity of compartments maintained?  Identity – marker molecules on cytosolic surface  Mechanisms – Coated vesicle  Coat – cage of proteins on cytosolic surface of vesicle  Regulation of vesicle formation o Lipids  Phosphoinositides – PI  Inisitol phospholipids plus phosphates  Different organelles have different PIs (Fig 13.11)  Different proteins will bind to different PIs by shape – adaptor proteins that bind to SPECIFIC PIs, and that initiates the formation of a clatherin coat  Interconversion of PU headgroups regulates formation Coats!  Functions o Concentrates specific proteins in a membrane o Shapes off vesicles  3 Major Types: o Clatherin – from PM between Golgi and Chromosomes  Figure 13.48  Endocytosis – from PM to cell  Clatherin triskelion – 3 feet  Spontaneously self assemble into a cage  Cargo receptors – transmembrane proteins that bind to cargo  Adaptor receptors – bind receptors and clatherin  Coat is removed after vesicle forms  DIFFERENT ADAPTINS allow different cargo receptors to be transported  Adatins select receptors, receptors select cargo  Dynamin protein pinches off the vesicle, using GTP (GTAase)  HSP70 (ATPase) – use ATP to remove the dynamin coat o COP I – Between golgi compartments o COP II – from ER to Golgi  Coat-recruitment GTPases o GTP-bindin
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