MCBG 9 - protein sorting Flashcards Preview

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Flashcards in MCBG 9 - protein sorting Deck (23):
1

Protein sorting. How do proteins go to ER? SIGNAL AND RECEPTOR
Energy
Where is the protein made?
Specific proteins
Fully folded on entering

KDEL
KDELR -> COPI coat
No
RER
No
YES

2

Protein sorting. How do proteins go to lysosomes? SIGNAL AND RECEPTOR
Energy
Where is the protein made?
Specific proteins
Fully folded on entering

MP6 -Mannose-6-Phosphate
and peptide signal patch
MP6R
ATP proton pump
ER
No
YES

3

Protein sorting. How do proteins go to Nucleus? SIGNAL AND RECEPTOR
Energy
Where is the protein made?
Specific proteins
Fully folded on entering

NLS - Nuclear localisation signal
Binds to Importin (a&B)
Yes - GTP-GDP for Ran
Cytoplasm
Yes RAN
Yes

4

Protein sorting. How do proteins go to Mitochondria? SIGNAL AND RECEPTOR
Energy
Where is the protein made?
Specific proteins
Fully folded on entering

Mitochondrial transport signal
TOMS/TIMs
ATP
cytosplasm
MSF (chapperone proteins prevent it from folding)
No

5

Which codon specifies the first amino acid in any protein?

AUG

6

How might antibiotics work to inhibit translation?

Block binding of tRNA (tetracyclin), prevent peptide bond formation (chloramphenicol) , stop translocation (erythromycin

7

What two processes may be need to occur to a protein after translation?

Proteolytic cleavage and chemical modification

8

Where are proteins destined for the membrane or secretory pathway synthesised?

Ribosomes on RER

9

Where are Protein destined or cytosol, or postranslational import into organelles synthesised?

Free ribosomes (cytosol)

10

What are the four things that are needed for protein sorting?

Signal intrinsic to the protein, receptor to recognise it, translocation machinery, energy

11

What are the two types of exocytosis out of the cell from the golgi

Constitutive
Regulatory

12

What modification occurs in the ER? 3.

Signal cleavage (proteolytic cleavage),
Disulphide bond formation,
N-linked Glycosylation
Folding
Assembly of subunits

13

What modification occurs in the Golgi body? 3.

O-linked glycosylation (sugar [glycosyl transferase]-> SER/THR),
Trimming/Modification of N-linked sugar,
Proteolytic processing

14

Why would a protein be made in a non-active form.

Proteins like lysosomes need to be exocytosised
Some may be too large

15

How does a protein know its destined for the peroxisome? Which terminus?

Initial targeting sequence (Peroxisome targeting sequence)
C

16

What is the name of the peroxisome receptor

PTS receptor Pex5

This binds to cargo protein in cytoplasm

17

Protein sorting. How do proteins go to Peroxisome? SIGNAL AND RECEPTOR
Energy
Where is the protein made?
Specific proteins
Fully folded on entering

Peroxisome targeting sequence PTS
Pex5 - binds ot cargo protein in cytoplasm, Binds to Pex5 on outside of peroxisome
Yes - to recycle the PTS receptor

18

Name a peroxisome transport disorder

Zellweger syndrome

19

Give an example of Regulated secretion

Endocrine cells – secreting hormones
Exocrine cells – secreting digestive juices
Neurocrine cells – secreting neurotransmitters

20

What is the enzyme that produces disulphide bonds?

disulphide isomerase

21

What happens if mis-folding can not be corrected? 2

Protein may be returned to cytosol for degradation

Protein may accumulate to toxic levels in the ER resulting in disease

22

What happens if there are folding problems? 1

ER chaperone proteins attempt to correct problem

23

Whats the process of Insulin formation?

RIBOSOME - Pre-proinsulin is translated
ER - Initial sequence cleaved. Di-sulphide bonds, Proteolytic cleavage = Proinsulin
GOLGI - Takes proinsulin and cleaves the pro part. Leaves you with two polypeptide chains parallel with three disulphide bonds