Polvi lec#11

Question 1

What do COP11 coated vesicles do?

Answer 1

These move cargo forward, from the ER to the golgi complex
They select and concentrate for certain proteins to be transported in vesicles by interacting with receptors that recogjnize transmembrane protein ER export signals

Question 1

What are the three types of coated vesicles?

Answer 1

COP1-coated vesicles, COP11-coated vesicles, and Clathrin-coated vesicles

Question 2

What does COP11 gather and concentrate?

Answer 2

Enzymes destined for the golgi
proteins involved in vesicle docking and fusion
proteins that bind soluble cargo and proteins that should be secreted

Question 3

What is Sar1? How does it work?

Answer 3

Is a cop11 coat protein, it takes ona diff confirmation depending on whether it’s bound to GDP or GTP
Sar1-GDP goes through a confirmational change and becomes Sar1-GTP through the guanine exchange factor, Sar1-GTP gets inserted into the cytoplasmic leaflet which bends the membrane
Sec24 dimer is an adaptor protein that interacts with the ER export signal of the membrane protein, this further bends the membrane
a cage is formed around this complex and the complex is then disassembled by hydrolysis of GTP bound to Sar 1

Question 4

What are COP1 coated vesicles?

Answer 4

These allow cargo to move backwards from golgi to er, and trans golgi to cis golgi.
COP1 is made of a protein complex called coatamer which forms a thick protein coat directly on the membrane

Question 5

What is Arf1?

Answer 5

Is a cop1 coat protein, when bound to GTP it inserts into and bends the membrane

Question 6

How do COP1 coated vesicles transfer things back to the ER proteins?

Answer 6

Proteins in the ER contain a retrieval signal which cop1 detects

Question 7

What are the two types of retrieval signals that Cop1 recognizes? Is there other signals outside of this?

Answer 7

KDEL- is on soluble ER proteins and is recognized by a KDEL receptor that cop1 interacts with
KKXX- is on ER membrane proteins
they are other retrieval signals which are based on the compartment of the endomembrane system your in

Question 8

How does vesicle fusion work?

Answer 8

1. Vesicles are moved to target compartments by microtubules and motor proteins
2. Vesicles are tethered to the target compartment by tethering proteins (can be rod shaped or a multiprotein complex)
3. G proteins called Rabs specify this procedure by recruiting specific tethering proteins for each vesicle and interacting with specific motor proteins to move vesicles to certain areas
4. V SNARE proteins (put into transport vesicles during budding) and T-SNARE proteins (located in the target mebrane) form a complex
5. This complex fusion results in vesicle and target mebrane to fuse ther lipid bilayers and vesicle releases cargo inot target membrane.

Question 9

Lysosomes contain how many hydrolytic enzymes?

Answer 9

at least 50, enzymes here have an optimal activity in acidic pH’s

Question 10

How is the ph of the lysome maintained?

Answer 10

through the V-type proton pump H+ ATPase