General Molecular Chaperone Action and Chaperone Networks

Question 1

What is a molecular chaperone and why do some proteins need them?

Answer 1

• Large and diverse group of proteins that assist the folding/unfolding and the assembly/disassembly of other macromolecular structures
• They are not permanent components of the folded structures

Question 2

Chaperones required to prevent ?

Answer 2

Irreversible non-native (incorrect) hydrophobic amino acid interactions cause folding to stall = Complex folding pathway

Question 3

Incorrect interactions that are non-reversible cause ?

Answer 3

The folding to stall in energy traps

- Chaperones avoid or allow escape from these energy traps

Question 4

Name holder chaperones ?

Answer 4

ATP independent:
- sHsp
- Trigger factor 
- Prefoldin 
ATP dependent:
- Hsp70

Question 5

Name unfolder chaperones ?

Answer 5

ATP dependent:

• Hsp60
• Hsp100

Question 6

Name folder chaperones ?

Answer 6

ATP independent:
- Calnexin
- Calrecticulin
- Protein disulphide isomerase
ATP dependent:
- Hsp90

Question 7

Explain the process of a holder chaperone ?

Answer 7

1. Protein is denatured or newly synthesised
2. Chaperone bind hydrophobic residues
3. Prevents irreversible aggregation
4. Cycles of binding and release allow refolding

Question 8

Where are Prefoldin (holder) present in ?

Answer 8

• Present in Archaea and Eukaryotes only

- A heterohexameric molecular chaperone

Question 9

Archaea generally lack Hsp70 but prefoldin ?

Answer 9

Can substitute for Hsp70 activity

Question 10

LOOK AT THE SLIDES

Answer 10

FIND SOME READINGS