ANAT 261 Study Guide - Midterm Guide: Hsp60, Hsp70, Keyboard Shortcut

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Midterm Review
Review Questions
Protein Folding Review Questions:
A mutation in a cytosolic protein from F to C results in a protein that does not fold correctly. Why?
decrease hydrophobicity results in core of protein not established and thus destabilized structure.
-No sulphide bond formation in cytosol (reducing)
-Loss of F disrupts binding of proteins with partner and thus disrupts quaternary structure.
-Less suitable substrate for chaperones
-F is key binding residue for hydrophobic ligand that’s required for folding
-Protein able to form non-specific interactions between the C and cellular components. These impede
proper folding.
Differentiate between the 3 chaperone families:
all are ATP dependent, use to control substrate binding and release
-ATP-bound states bind substrate for Hsp70, but not Hsp60 or 90
-All target hydrophobic residues
-Only Hsp70s require co-chaperones
-Targets: Hsp70-versatile (short stretches and unfolded proteins), Hsp90 (proteins closer to native state).
Hsp60 can only target small proteins, usually nearer to the native state.
Uses:
- Hsp70 used to fold newly synthesized proteins and proteins being translocated to the ER and
mitochondria.
- Hsp90 key mediator of heat shock response (with HSF1)
- HSP70 and 90 are used to stabilize hormone receptors.
- Hsp70 and 90 used to shuttle unfolded/TM domains from the ribosome to mitochondria
- Hsp70 and 90 both associated with TPR domains
The ability of the COPII coat to interact with its cargo is lost. In the (unlikely) event that the cell
survives this. What would you expect to happen?What about COPI?
COPII responsible for anterograde direction
-The inability to recognize ER exit signals prevent rapid export of cargo
-default flow through secretory pathway is to go to PM, so anterograde is still possible, although slower
-In contrast, retention signals required to keep changes in ER or golgi. Without recognition by COPI,
retrograde transport will be effectively lost.
-But, interaction of adaptor proteins with cargo in both cases important to get vesicles to actually form, so in
reality we would expect all COP transport to be severely impaired or lost.
The six types of transporters in mitochondrial import and energy requirements:
Tom 40 and Tom 20- affinity gradient only
-Tom40 with Tom70 (IM proteins)- cytosolic ATP to cycle chaperones
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