Lecture 18:

Question 1

How does the cell deal with misfolded proteins

Answer 1

If newly made proteins do not fold properly, they cannot function properly and may damage the cell. Also, fully-formed proteins can denature by heat and other insults.

A number of proteins, known generically as chaperones, associate with the nascent (growing) polypeptide as it emerges from the ribosome – either in cytoplasm, or in ER
Chaperones facilitate the proper folding of the polypeptide by suppressing or unfolding ‘incorrect’ structures
Two common types of chaperone proteins are Hsp70 and chaperonin (in diagram above)
If the mis-folded proteins cannot be corrected, they are exported out of the ER and destroyed by the proteasome (or… are just destroyed by the proteasome if the protein was made in the cytosol).