4 Membrane Protein Targetting Flashcards Preview

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Flashcards in 4 Membrane Protein Targetting Deck (22)
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1
Q

where does translation for every protein begin?

A

in the cytoplasm

2
Q

proteins that are completely translated in the cyotplasm can end up where?

A

nucleus

  • mitochondria
  • cytoplasm (this is the default)
  • peroxisomes
3
Q

where can proteins that are translated on the ER end up?

A
  • ER
  • plasma mem
  • secretory vesicles
  • lysosomes
  • golgi
4
Q

what are the characteristics of signal sequences which direct proteins into the nucleus after translation?

A

short and basic (lots of lys residues)

5
Q

what are the cahracteristics of signal sequences which send proteins to the mitochondria?

A

they are a very long sequence of aa and are found on the N terminus

6
Q

where does the SKL signal sequence direct proteins to?

A

peroxisomes

7
Q

what does the KDEL sequence mean when found on a tranlated protein? what is the clinical significance?

A
  • the protein will return to the ER

- a mutation in this region can result in dialted cariomyopathy

8
Q

what protein type are inducible by high temps and what subcategory falls within this?

A
  • heat shock proteins

- many chaperon proteins are heat shock proteins

9
Q

what binds unfolded, misfolded, and aggregated proteins and chaperones them to the proteasome for degradation?

A

chaperon proteins

10
Q

neonatal adrenoleukodystrohpy and zellweger syndrome are examples of what type of disease?

A

defective peroxisomal targetting

11
Q

T/F many ribosomes trasnlate a single mRNA strand at once on the ER membrane

A

True

12
Q

what happens to a protein that is destined to be secreted once it is translated on the ER membrane

A
  • is it is being translated, it is entering the ER lumen
  • once translation is completed, the signal peptide is cleaved (not incorporated into final protein product)
  • protein released into lumen, signal peptide remains in membrane, plug covers up ER pore
13
Q

Once a protein that is destined to be a transmembrane protein begins to be translated on the ER membrane, what happens?

A

-once a stop transfer sequence (very hydrophobic) reaches the ER membrane, it stays in that location and either another loop is formed or the C terminus remains in the cytoplasm. Remember that the n terminus is where the start transfer sequence resides

14
Q

where is the start sequence located on a protein that is destined to be a transmembrane protein?

A

N terminus (this is the first part of the protein that gets trasnlated)

15
Q

Does translation of proteins occur in the golgi?

A

No, only in the ER

16
Q

what occurs in both the ER and the golgi? in a general sense

A
  • protein sorting

- addition and trimming of sugars

17
Q

where does phosphorylation of lysosomal proteins occur?

A

ONLY in the cis-golgi

18
Q

lysosomal enzymes work best in basic conditions, T/F

A

False, these is a proton pump on the membrane of every lysosome that maintains an acidic environment inside the lumen

19
Q

what is the typical pH within a lysosome?

A

about 5

20
Q

if a protein is programmed to end up in the lysosome, what happens once it is translated in the Rough ER?

A

it is sent to the cis golgi where it is phosphorylated with a MANNOSE 6 PHOSPHATE, then a clathrin coated pit is formed which buds off of the trans-golgi, eventually the clathrin is lost, the M6P buds off and is recycled, and this either becomes a new lysosome or fuses with an existing one

21
Q

can secreted protein get sent to the lysosome?

A

yes, they can bind to M6P receptors on the cell surface, endocytosed, and sent to the lysosome

22
Q

what disease revealed the pathway in which proteins are targeted to the lysosome?

A

I cell disease, thisis caused by dysfunction in the phoshotransferase which tagged lysosomal proteins with M6P
-These patient’s lysosomes were full of inclusion bodies which had protein, fat, and carb in them which mean the lysosome was missing all of its enzymes.