Lecture 17 - Intracellular Vesicular Traffic Flashcards
What are the different vesicular transport pathways?
- biosynthetic-secretory
- endocytic
- retrieval
What factors affect where a vesicle will go?
- membrane composition
- molecular markers in the membrane
What are the major functions of the coat in coated vesicles?
- concentrates selected proteins
- molds and shapes vesicle
What are the different types of coating molecules and what direction of transport are they associated with?
COPI:
-transport from Golgi cisternae; typically retrograde
COPII:
-transport from ER; typically anterograde
Clathrin: transport from Golgi apparatus and plasma membrane
Describe the structure of clathrin coated vesicles.
- clathrin subunits consisting of 3 large chains and 3 small chains forming a 3-legged triskelion
- triskelions form a basket-like structure which gives shape to the vesicle
- adaptor proteins connect clathrin and cargo proteins to the cell membrane
What role do phosphoinositides play in vesicular transport?
- used in coat assembly, vesicle formation, and protein trafficking
- different combination of phosphorylation at the 3’, 4’, and 5’ which are organelle and domain specific
- control recruitment and binding of proteins
Each organelle has its own set of __________ and __________ which convert phosphoinositides to be specific to that organelle.
PI kinases and phosphatases
What are BAR domains?
- protein coils which form dimers that have a positively charged inner surface
- inner surface interacts directly with negatively charge phosphate heads on cell membrane causing it to bend
What is dynamin?
- ring structure which assembles at the base fo a clathrin bud
- contains a PIP2 binding domains which binds the cell membrane
- contains a GTPase domain regulates rate of pinching
- recruits proteins which pinch bud off
What is HSP 70?
-chaperone protein which uses ATP to remove vesicle coat
What are Rab proteins?
- monomeric GTPases (~60 types)
- active in GTP bound form (membrane/GEF bound)
- inactive in GDP bound form (cytosolic/GDI bound)
- acts as a marker for certain compartments
- activated Rab bind Rab effectors (tethering proteins)
What organelle(s) are Rab1, Rab3A, and Rab5 located on?
Rab1:
-ER and Golgi
Rab3A:
-secretory vesicle and synaptic vesicles
Rab5
-early endosomes, plasma membrane, and clathrin-coated vesicles
What are SNARE proteins?
Types:
- v-SNARE: located singly on vesicle membrane
- t-SNARE: located in group of 2-3 on target membrane
- trans-SNARE: fully associated v and t-SNARE complex
-v and t-SNARE associate and pull vesicle to target membrane allowing them to fuse
What is NSF?
- protein which separates trans-SNARE complex using ATP
- allows v-SNARE and t-SNARE to be reused
What mechanism is used by many viruses to invade host cells?
-fusion with cell membrane via mechanism similar to SNARE
