Heat Shock Proteins & Protein Folding: How HSP Helps

[Priyadarshini]

I was watching a video in which they said that HSP is produced to help proteins fold correctly and to prevent them from tangling up and misfolding. But, if the cell is producing another protein, wouldn't the chances of tangling up and misfolding increase (because now you have one extra protein to the already crowded cell cytoplasm), even though this other protein (HSP) is produced to aid proteins fold correctly?

 

[jim mcnamara]

HSP's do two "things":
1. chaperone newly synthesized proteins to allow correct folding
2. help stress damaged proteins return to the correct folded state.
so, we can say they are very targeted and work only with certain proteins in defined states of disarray.
They are increased in number post-stress events.

So particular HSP's are active only for certain protein species, and only under certain circumstances. They are not mass intruders into cytoplasm, attacking any and every wandering protein.
Try:
https://en.wikipedia.org/wiki/Heat_shock_protein

 

[Ygggdrasil]

During stress, cells often dramatically change which mRNAs get translated. Most translation in eukaryotic cells occurs through cap-dependent mechanism that rely on recruiting the ribosome to mRNAs containing a specific modified nucleoside at the 5' end of the mRNA. Under conditions of stress, the cell will decrease cap-dependent translation and instead prefer to perform cap-independent translation, which recruits the ribosome to specific mRNAs through other means (not all of which are well understood). Not all mRNAs can be translated in a cap-independent way, and many of the mRNAs that undergo cap-independent translation are involved in stress responses (such as the heat shock proteins). Therefore, because conditions of stress decrease cap-dependent translation, fewer proteins overall get translated. This decrease in translation helps ensure that the newly synthesized proteins get folded correctly by the limited pool of existing chaperone proteins.

(I'm not sure if the same applies to bacteria as capping is specific to eukaryotes)