4 Membrane Protein Targetting Flashcards Preview

Cell Biology > 4 Membrane Protein Targetting > Flashcards

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

where does translation for every protein begin?

in the cytoplasm

2

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

nucleus
-mitochondria
-cytoplasm (this is the default)
-peroxisomes

3

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

-ER
-plasma mem
-secretory vesicles
-lysosomes
-golgi

4

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

short and basic (lots of lys residues)

5

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

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

6

where does the SKL signal sequence direct proteins to?

peroxisomes

7

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

-the protein will return to the ER
-a mutation in this region can result in dialted cariomyopathy

8

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

-heat shock proteins
-many chaperon proteins are heat shock proteins

9

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

chaperon proteins

10

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

defective peroxisomal targetting

11

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

True

12

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

-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

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

-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

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

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

15

Does translation of proteins occur in the golgi?

No, only in the ER

16

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

-protein sorting
-addition and trimming of sugars

17

where does phosphorylation of lysosomal proteins occur?

ONLY in the cis-golgi

18

lysosomal enzymes work best in basic conditions, T/F

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

19

what is the typical pH within a lysosome?

about 5

20

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

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

can secreted protein get sent to the lysosome?

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

22

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

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.