Lecture 17 Flashcards
True or False: Vesicular transport is Bidirectional
True
it is technically both directional and bidirectional (retrieval pathways are what makes it bidirectional)
What determines where a vesicle will end up and how it gets there?
the composition of it’s membrane and molecular markers on the surface of that membrane AND complementary receptors on the target membrane.
describe the location of the coat on coated proteins
on the cytosolic side of the membrane
What are the 2 major functions of the coat on coated vesicles?
Concentrates selected proteins for transport
Molds the vesicle to form a basket-like lattice (gives shape to the membrane)
The coat is _____ when the vesicle reaches the target membrane
discarded
What is the function of COPI?
mediates transport from the golgi cisternae
What is the function of COPII?
Mediates transport from the ER
What is the function of Clathrin-coated vesicles?
mediates transport from the golgi and from the plasma membrane
Describe the structure of a clathrin subunit and give the term that describes the structure they form.
3 large and 3 small polypeptide chains that come together to form a “3 legged structure” called the
Triskeleton
where are triskeleton’s found, and describe their structure in geometric terms.
Found on the cytosolic side of the membrane
basket-like structure of hexagons and pentagons that form coated pits
in clathrin coated vesicles, what forms the second layer between the clathrin cage and the membrane-bound cargo receptors?
adaptor proteins
Assembly of a protein molecule coat induces what effect on the membrane?
curvature
what type of recuitment of membrane and cargo molecules occurs in a vesicle?
selective
what are cargo receptors bound to?
cargo molecules on one end and adaptor proteins(which will be attached to a clathrin subunit) on the other
What family of molecules plays a major role in coat assembly, vesicle formation, and protein trafficking?
Phosphoinositides (PI)
What do different organelles have in order to facilitate interconversion?
unique sets of PI kinases and Phosphatases
What is the purpose of Phosphatidylinositol?
interconversion occurs to change it between various phosphoinisitides to control the recruitment and binding of adaptor proteins for the specific needs of that organelle/domain.
Define what interconversion is
rapid cycles of phosphorylation and dephosphorylation at the 3’, 4’, and 5’ positions of phosphoinositides to form various derivatives.
What part of Phosphoinositides is recognized by proteins?
the head group (inositol to be exact) that serves as a “signature”
What are BAR domains?
proteins with “coiled coils” that bend membranes
How do BAR domains bend membranes?
they have a positively charged inner surface that interacts with the negatively charged lipid head groups of the membrane (bends it)
What removes clathrin coats from vesicles? how does this process happen?
Dynamin removes clathrin coats by first forming a ring around a clathrin bud.
The PIP2 binding domain and GTPase domain help “pinch” the membrane together
Dynamin recruits other proteins to “distort the lipid bilayer” and the vesicle looses it’s coat.
Once dynamin recruits other proteins to distort the lipid bilayer, how are the adaptor proteins unbound?
PIP2 is degraded once the vesicle looses it’s clathrin coat and that weakens the binding of adaptor proteins.
what protein physically peels off the clathrin coat?
HSP 70 chaperone protein and it uses ATP to do this
