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MSF1 > Protein Folding 2 > Flashcards

Protein Folding 2 Flashcards

1
Q

What are two types of chaperonin proteins?

A

Type I and Type II.

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2
Q

Where are Type I chaperonins found?

A

Bacteria, mitochondria and chloroplasts - GroEL/GroES

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3
Q

Where are Type II chaperonins found?

A

Archaea and eukaryotes

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4
Q

What does HSP90 do in eukaryotes?

A

Facilitates late stage folding of signalling factors.

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5
Q

What do nucleoplasmins do?

A

Assemble nucleosomes.

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6
Q

What does HSP70 do?

A

Reverses denaturation/aggregation through forming a complex with HSP40.

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7
Q

How many proteins are in the E. coli 30S subunit and what rRNA is associated with it?

A

21 proteins and 16S rRNA

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8
Q

How many proteins are in the E. coli 50S subunit and what rRNA is associated with it?

A

31 proteins, 23rRNA and 5S rRNA

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9
Q

How much of the E. coli ribosome is RNA?

A

~2/3

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10
Q

Where do newly synthesised proteins leave the ribosome through?

A

Narrow tunnel - peptidyl transferase centre (PTC).

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11
Q

In elongation what are nascent protein chains sensitive to and why?

A

Aggregation and degradation - because emerge unfolded from ribosome.

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12
Q

Can co-translation folding occur in both prokaryotes and eukaryotes?

A

Yes.

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13
Q

Are trigger factors ATP dependent?

A

Yes

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14
Q

What 2 activities do trigger factors possess?

A

Chaperone and prolyl-cis-trans-isomerase activities.

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15
Q

Which protein of the ribosome does the trigger factor have affinity for?

A

L23

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16
Q

How does the trigger factor prevent proteases cleaving the nascent polypeptide?

A

Binds to L23 protein closing the channel and protecting the chain.

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17
Q

What happens once translation terminates?

A

Trigger factor either dissociates if protein can fold itself or passes polypeptide to DnaK (HSP70 in eukaroyotes).

18
Q

What does DnaK do?

A

Decides if protein is to be folded (GroEL) or degraded.

19
Q

What type of chaperone is GroEL/GroES?

A

Type 1

20
Q

What part of the protein is GroES?

A

the caps.

21
Q

How many proteins in each layer of GroEL?

A 
7 proteins 
(3 layers = 21 proteins)
22
Q

What are the two conformations of GroEL?

A

Cis and trans

23
Q

Which is elongated cis or trans?

A

Cis

24
Q

Which conformation do unfolded proteins bind to and why in GroEL?

A

Trans - attracted to hydrophobic patches.

25
Q

What happens once protein has bound to trans GroEL?

A

There is affinity for GroES (cap) to bind.

26
Q

What binds alongside GroES?

A

ATP.

27
Q

What does capping (GroES) cause?

A

Cis conformation to form.

28
Q

How many ATPs are hydrolysed and what are they for?

A

7 and to assist protein folding?

29
Q

When can (2nd chamber) trans conformation bind a polypeptide?

A

Once ATP has been hydrolysed.

30
Q

What are the main targets of GroEL/GroES?

A

Alpha beta proteins.

31
Q

How is selectivity determined in GroEL/GroES?

A

By size - there is limitation on what can fit.

32
Q

What is a heat shock protein?

A

Type of chaperone protein.

33
Q

When are HSPs expressed?

A

In heat shock stress - when cell becomes damaged due to aggregation.

34
Q

What can HSPs do?

A

Sequester proteins from aggregates that can be still be refolded.

35
Q

Describe function of PDI?

A

Randomises disulphide bonds (disrupts them) - when protein is correctly folded disulphide bonds will be protected. So assists protein in finding most stable conformation.

36
Q

What is the rate limiting step of protein folding often?

A

Cis-trans prolyl isomerisation.

37
Q

How does PPI accelerate cis-trans prolyl isomerisation?

A

Twists peptide that C,N,O atoms are no longer planar. (accelerates by 100 fold).

38
Q

What is the pH of lysosome and how is it maintained?

A

5.5 and maintained by ATPase proton pump.

39
Q

What proteins does lysosome normally degrade?

A

Extracellular proteins.

40
Q

Which protein binds proteins that are tagged to be degraded by lysosomes?

A

Hsc73 - constitutively expressed HSP70 chaperone.

41
Q

What protein does Hsc73 interact with?

A

LGP96 on lysosome membrane.

MSF1 (12 decks)

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