protein sorting

Question 1

What signal does mRNA to pass deom nucleus to cytoplasm

Answer 1

5’cap

Question 2

what mechanism do proteins use to enter the nucleus

Answer 2

The Nuclear Localization Signal: a 7-20 A.A. stretch high in basic Amino Acids

Question 3

How does the Nuclear Transport Receptor work and how is it different from most of the receptors we’ve previously discussed?

Answer 3

Nuclear localization signal binds to nuclear protein.
Pair binds to Nuclear transport receptor (that is floating free)
Receptor-ligand pair can cross nuclear pore complex.
different because these are free floating and act as a pass into nucleus

Question 4

How was the Pulse-Chase experiment used to track the synthesis and movement of secretory proteins?

Answer 4

Active cells were Pulsed cells with radioactive amino acids. Radioactive amino acids get incorporated into transcription and follow where they go. Chase with non-radioactive amino acids to stop radioactive incorporation. (turn off signal to follow original signal)

Question 5

• How are proteins destined for secretion, or transport via vesicles to other parts of the cell inserted into the ER lumen?
  What affect does this process have on the ribosomes themselves?
  What additional proteins are involved?
  What happens to the signal sequence?

Answer 5

1. Tell ribosomes to pause translation
2. Drag complex to ER membrane and bind to SRP.
3. SRP binds to SRP receptor on ER
4. Translation starts again and SRP is released.
5. Once protein is complete, signal sequence is removed by proteins.

Question 6

Be able to model a protein that has its N- or C-terminus on different sides of the membrane, or with different amounts of transmembrane domains.

Answer 6

N terminis will be closer to ER sognal seqence.
Ceterminis closer to stop sequence:
Have different transmembrane proteins depending on where signal and stop signal is.

Question 7

Unfolded Protein Response – be able to describe the UPR, and its relationship to signal transduction and gene expression.

Answer 7

1. Proteins translation into the Er
2. Chaperones assist in folding
3. too many unfolded proteins overwhelp ER
4. Binding to receptor start signal transduction pathway
5. relay molecules induces transcription factors
6. TF arrive in nuclues and turn on cchaperone genes
7. creation of more chaperon proteins
   new chaperones fix unfolded protein and signal pathway turned off from lack of ligand

Question 8

Be able to describe in general terms how cells label individual proteins with a “shipping label”.

Answer 8

Enzymes add specific sugars to protein. Code the proteins as they come into the golgi
Sugars added or trimmed to protein to target specific vesicles

Question 9

Be able to describe how these labelled proteins get to the appropriate vesicle in the Golgi.

Answer 9

Enzymes: Receptors on golgi are specific to those sugars
move through motor proteins

Question 10

Be able to describe how these vesicles are transported to and fuse with the target membranes.

Answer 10

Vesicle comes to target membrane, twist snares togther have the vesicle fuse with membrane and spill content

Calcium dependent