Biochem Accessory Folding
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What does PDI stand for?
Protein disulfide isomerase
Where is PDI found?
What does PDI do?
Catalyzes disuflide bond breaking and reformation, until a stable structure is reached
What form must PDI be in to function?
Its oxidized form
What are the four key residues in the active PDI domains?
What is the purpose of the second Cys?
To detach a peptide bound Cys and allow reformation
What is the fold adopted by PDI's domains?
A thioredoxin fold
How many domains does PDI have, what are their names?
- - Alpha + Alpha'
- - Beta + Beta'
What does PPI stand for?
Peptidyl prolyl cis-trans isomerase
What are the five Molecular Chaperones?
- 1. Heat Shock Protein 70
- 2. Trigger Factor
- 3. Chaperonin
- 4. Heat Shock Protein 90
- 5. Nucleoplasmins
What are chaperonins?
- Large multisubunit cagelike assemblies
- - ATPases, GROEL/ES (Group i), CCT/TriC (Group ii)
What are the four domains of GroEL?
Apical, Intermediate and Equatorial
What is the size and structure of GroEL?
14 Identical Subunits, 60 kDa each
What is the size and structure of GroES?
Seven Identical Subunits, 10 kDa each
Where is GroEL/ES found?
Which domain is responsible for ATP hydrolysis?
How big is GroEL's central cavity? What separates the two subunits?
- 45 Angstroms
- The N and C termini
What changes occur with GroES binding?
- - Large concerted movements
- - Cavity volume doubles with widening and elongation
- - ATPase activation
What to the Apical helices initially bind to in GroEL?
The unfolded protein
What causes the apical helices to detatch from their initial companions in GroEL?
Why is stealing of the apical helices important for GroELES?
Deprives substrate protein of binding sites, allow folding
Generally, how many ATP bind to GroEL? When do they bind?
Seven, before GroES association
When does the misfolded protein bind to GroEL?
After ATP binding
What triggers ATP association?
ATP hydrolysis on the trans ring (ADP present)
When does bound ADP dissociate?
With GroES binding to the trans ring
What triggers ATP hydrolysis?
No specific trigger, occurs after GroES binding, and ADP release
How long does ATP hydrolysis take?
What triggers GroES release?
Hydrolysis of ATP weakens GroEL/ES association
What are the two models for Protein folding?
- Anifsen Cage
- Iterative Anealing
Explain the Anifsen Cage model
- - GroEL/ES provides the perfect microenvironment
- - Small volume of cage means less room for error
- - Hydrophillic walls prevent burying of hydrophobes
Explain the Iterative Annealing Method
- - ATP unfolded and refolded by stretching apical domain (helices)
- - Stretching and subsquent release removes protein from local minima
What are Eukaryote GroEL/ES-like proteins?
Group II chaperonins
What are some characteristics of Group II chaperonins?
- - Eukaryotes
- - Two rings, 8-9 subunits
- - ATPase
- - No lid (like GroEL/ES)
- - Lid formed from helical extensions
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