Intracellular Vesicular Traffic 1 Flashcards
vesicular transport mediates a continuous _______ of components between various membrane enclosed compartments
exchange
What gives each compartment its full molecular address?
combination of markers
________ pathways return molecules to source
retrieval
Cells _______ proteins into membrane domains by assembling a special ______ on cytosolic side of the membrane
segregate; coat
What are the two major functions of coats?
concentrates select proteins in a specialized path for transport
models the vesicle to form a basket like lattice that deforms the membrane and gives shape to the vesicle
What are the types of coated vesicles?
COPI
COPII
Clathrin
COPI mediates transport from ______
golgi cisternae
COPII mediate transport from ______
ER
Clathrin coasted vesicles mediate transport from ______ and ______
Golgi apparatus
plasma membrane
Each clathrin subunit has how many polypeptide chains? and what does it form?
3 large and 3 small chains
form three leg structure called triskelion
Triskelions assemble into a __________ structure of hexagons and pentagons that form coated pits on the ______ side of membrane
basket like
cytosolic
What forms a second layer between the cage and the membrane in clarthrin coated vesicles?
adaptor proteins
assembly of the coat protein molecules introduces a ______ in the membrane
curvature
After the curvature forms in the membrane, what happens?
formation of coated buds
______ proteins bin clathrin and membrane bound cargo receptors
adaptor
After vesicle formation is complete, what happens to the clathrin coat?
it is lost
What does phosphoinositides do?
play a major role in coat assembly, vesicle formation and protein trafficking
Where do phosphoinositides undergo phosphorylation and dephosphorylation? and what does it form?
at the 3’, 4’ and 5’ positions
forms various derivatives
Interconversion between various phosphoinositides is highly compartmentalized, _______ specific and ______ specific
organelle
domain
Different organelles have unique sets of ________ and ______ to facilitate inter conversion
PI kinases
phosphatases
When removing the clathrin coat, what protein assembly around the clathrin bud?
dynamin
What domains does dynamic contain?
PIP2 binding domain
GTPase binding domain
What does the PIP2 binding domain do?
tethers the protein to membrane
What does the GTPase binding domain do?
regulates rate of vesicle pinching
What does pinching do?
brings the 2 cytosolic sides of the membrane together and allows them to fuse
What protein uses ATP to peel off the clathrin coat?
HSP 70
What do Rab proteins do?
direct vesicle to specific spots on target membrane
What do SNARE proteins do?
mediate fusion of vesicle with membrane
What are Rab proteins actively regulated by?
GTPases
Each Rab is ______ with one or more membrane compartments of the secretory or endocytic pathway
marker
Rab is inactive in what form? active?
inactive: GDP bound
active: GTP bound
What happens when bound to Rab-GDP dissociation inhibitor?
keeps inactive GDP bound form, form is soluble
Where is Rab1 located?
ER and golgi complex
Where is Rab3A located?
synaptic vesicles, secretory vesicles
Where is Rab5 located?
early endosomes, plasma membrane, clathrin coated vesicles
What do SNARE proteins do?
catalyze fusion of vesicles with membranes
How many different SNAREs are there?
35
where are v-SNAREs found?
vesicle membrane
Where are t-SNAREs found?
target membranes
When v and t SNAREs interact, what happens?
wrap around each other to form a bundle
Newly synthesized proteins are packaged into ________ coated transport vesicles.
COPII
How does quality control occur in transport from ER?
incomplete/misfolded proteins are contained in the ER by binding to chaperone proteins such as BiP and calnexin, then proteins degrade
What is homotypic fusion?
fusion of vesicles from same compartment
What is heterotypic fusion?
fusion of vesicles from different compartment
What are fused structures called?
vesicular tubular clusters
What are the 2 faces of the golgi?
cis (or entry) and trans (or exit)
What is the Cis golgi network (CGN)?
network of fused vesicular tubular clusters arriving from ER. Proteins and lipids enter golgi via CGN
What is the trans golgi network (TGN)?
region that allows exit of proteins and lipids to next step fo secretory pathway
Golgi plays important role in protein______
glycosylation
