2.8 Intracellular Vesicular Trafficking 1 Flashcards
What are the 3 pathways for vasicular transport?
Secretion (from ER to cell membrane). Endocytosis. Retrieval/Recycling (cell membrane to ER).
What is the lipid anatomy?
Sugars,Phosphate, glycerol, and fatty acid tails.
What does the lipid composition of membranes help to do?
Determine organelle identity, define membrane curvature, selectively recruit trafficking-related proteins.
What are Rab proteins.
Monomeric GTPases
What do Rab proteins do?
Their regulation controls the progression of vesicular transport
What are the two forms of Rab?
Rab-GTP active and membrane bound. Rab-GDP inactive in cytosol.
What does Rab-GTP do?
Serve as scaffolds as connectors to catch and release other proteins (effector proteins) that catalyze or stimulate the processes as we move along
Why does Rab-GTP turn to Rab-GDP?
In order to be recycled.
What does GDI do?
Keeps Rab-GDP from interacting with membrane and keep it in the GDP formation until its back home.
Assembly of a protein coat on the cytosolic side of teh donor compartment membrane does what?
Shapes the budding vesicle and concentrates the cargo.
What are the 3 coats?
COPII, COPI, and Clathrin
COPII coats vesicles that move cargo from
ER to Golgi (anterograde)
COPI coats vesicles that move cargo from
Golgi to ER (retrograde)
Clathrin coats vesicles that move cargo from
golgi to endosomes or inward from cell membrane
Cant the NPC squeeze in a vesicle?
No
What is a good example of gene duplication?
Coat proteins similar features that have diversified.
How does the coat form?
Outer layer forms a cage, inner layer proteins interact with the donor plasma membrane. Inner and outer layers form sequentially.
How many layers do the coat proteins each have?
COPII has 2. COPI has 1. Clathrin has 2.
what stimulates uncoating?
GAP
For the coat proteins, what proteins initiate coating?
COPII: Sar1. COPI: Arf1. Clarithin: AP1/Arf1.
For the coat proteins, what initiates uncoating?
COPII: Sec23. COPI: ArfGAPs. Clathrin: AP2
What 3 things can cargo be?
Soluble, membrane associated, and tethering/fusion machinery
Where is the sorting sequences on the coating proteins?
COPII: cytoslic face. COPI: C term. Clathrin: Linear motifs
What is the cargo receptor for the coat proteins?
COPII: Sec 24. COPI: Arf 1: Clathrin: various adapter proteins.
What can start the budding process?
Gently bending, and actin.
What helps the budding process in the coat proteins?
COPII and COPI: coat polymerization. Clathrin: Actin.
What does pinching off require?
Protein factors that distort membrane curvature.
What proteins are needed for pinching off via the coat proteins?
COPII: Sar 1. COPI: Arf1. Clathrin: Dynamin +Epsin
what must vesicles be before they can ride the cytoskeleton to their destinations?
Must be uncoated
What energy is required to uncoat the coat proteins?
COPII and COPI: GTP hydrolysis. Clathrin: ATP hydrolysis.
What does Dynein and Kinesin do?
Dynein moves vesicles towards the cell membrane. Kinesin moves vesicles toward the nucleus.
What proteins do the coat proteins use to move?
COPII: Dynein. COPI: Kinesin and dynein. Clathrin: Kinesin
Once vesicles are at their destination, what happens?
We need to capture and fuse.
What do the tethering proteins and SNARE proteins do?
Bring vesicles close enough to target membrane for SNARE proteins to interact and initiate fusion.
how many SNAREs are there?
2
What is another good example of gene duplication?
SNAREs. One SNARE has 2 dif helices and divided into 2 seperate proteins.
What is the common structure for SNAREs?
They this 4 helices bundle that is primarily hydrophobic except in the middle.
True or False. T snares will usually be Q, V snares will usually be R.
true
True or False? Different compartments have different SNARE profiles.
True
Once fusion happens via the SNAREs what must happen in order to untagle the SNAREs?
Energy consumption.
