Chaperonins are for nascent proteins that don't fold independently or interact with other cytosolic chaperones
To what is the arrow pointing on the Gro-El monomer?
Apical substrate binding site
ATP binding site
How many monomers make up Gro-El?
14- 7 in each layer
12- 6 in each layer
10- 5 in each layer
Gro-Es is made of 7 monomers
Why does Gro-Es bind to close the cavity?
Creates a space away from crowded cytosol for protein binding
Creates a highly acidic environment for proteins to fold in
Allows protein to fold in highly saline environment
ATP & Gro-Es bind at separate points in the protein folding cycle
The nascent protein will bind at the monomer level _ side with ADP and Gro-Es bound
At the same
Once Gro-Es and ATP are bound, the protein refolds for _ seconds whilst the ATP is hydrolysed
When the protein has folded properly, what happens?
A nascent polypeptide binds to the end opposite the Gro-Es and ADP, causing the cycle to repeat itself at the other end of the protein
Gro-Es dissociates, releasing the folded protein
The ADP is released and replaced with ATP
The CCT and Gro-El cycles are basically the same, but Gro-El has flexible extensions that CCT does not
What is bacterial homologue of the Hsp100 family?
Hsp100 and its bacterial homologue are hexamers
Clp100 and its bacterial homologue do what?
Unfold proteins in the presence of ATP
Fold proteins in the presence of ATP
What is the difference between Class 1 & Class 2 Hsp100 proteins?
Class 1- Protein degredation
Class 2- Protein disaggregation and refolding
Class 1- Protein disaggregation and refolding
Class 2- Protein degredation
How do you tell apart Class 1 and Class 2
Class 1 has 2 ATPase sites, Class 2 has 1
Class 1 has 1 ATPase site, Class 2 has 2
Hsp100's consist of one/two sets of hexamers
The ATP is hydrolysed in Hsp100's/Clp proteins to allow what?
To drive conformational changes in aromatic loops that interact with the substrate
To provide energy to break the peptide bonds in the protein to be unfolded
To provide energy to posh apart poorly stacked peptides
When ClpA and ClpP interact, what is the role of the supercomplex?
Unravel denatured protein
Hsp90 chaperones are required for what?
High temperature growth
High salinity growth
High pH growth
Hsp90 are ATP dependent monomers
What is found on the N-terminus of a Hsp90 protein?
Substrate binding domain
The dimerisation domain of Hsp90 occurs at the C terminus
ATPase inhibitors of Hsp90 target which part of the protein?
The binding of ATP causes the ATP 'lid' to close and the dimer to split
Name the conformational changes that occur after ATP binds
N-terminals undergo Beta strand exchange
N-terminals undergo Alpha helix exchange
Rotation of N domain (relative to middle) to allow meeting of dimerisation domains
Rotation of C domain (relative to middle) to allow meeting of dimerisation domains
What is the role of the core domain of Hsp90 (with regards to the ATPase)
It's flexible enough that it completes the dimerisation site and allows ATP hydrolysis to occur
It's flexible enough that it completes the ATPase site and allows ATP hydrolysis to occur
Interacting with the gamma phosphate of ATP
The conformational changes of Hsp90 are thought to be brought about by client proteins
cd37/p50 inhibit Hsp90 by what process?
Binding it to Hsp70
Preventing N-terminal dimerisation
Phosphorylation of Hsp90
Sti/HOP bind to the N-terminal of Hsp90 & Hsp70, binding them together as a potent inhibitor
Aha activates Hsp90 how?
Activates ATPase activity by promoting open state of of catalytic loop
Causing N-terminal alignment for dimerisation
Physically holding the active site open
Spa1 both inhibits and stimulates ATPase activity, leading to an overall slowing of ATPase in Hsp90
How does Sba activate ATPase activity?
Interacts with the middle domain of Hsp90 and modulates the catalytic loop of this domain
Increases the affinity of the dimerisation sites for each other, completing the ATPase sites more stably
Increases the affinity for the binding site for ATP
Hsp90 can be used to activate steroid receptors and kinases