maintenance of unfolded protein

Definition

Target type: biologicalprocess

Maintaining a protein in an unfolded, soluble state. [GOC:bf, GOC:BHF, GOC:nc, GOC:PARL, PMID:21636303]

The maintenance of unfolded proteins is a critical cellular process that ensures the proper folding and function of proteins, while preventing their aggregation and degradation. It involves a complex interplay of molecular chaperones, folding enzymes, and proteases, working together to maintain protein homeostasis.

**Molecular Chaperones:** These proteins bind to unfolded or misfolded proteins, preventing aggregation and facilitating proper folding. They act like “nannies,” helping proteins find their correct shape. Some key chaperones include:

* **Hsp70:** Binds to unfolded proteins, preventing aggregation and helping them fold correctly.
* **Hsp90:** Assists in the folding of a wide range of proteins, including those involved in signaling pathways and stress responses.
* **Hsp40:** Acts as a “co-chaperone” to Hsp70, delivering unfolded proteins to it for folding.
* **Hsp60:** Forms a “barrel-like” structure that helps to refold misfolded proteins.

**Folding Enzymes:** These enzymes catalyze specific modifications to unfolded proteins, facilitating their correct folding. Some examples include:

* **Peptidyl prolyl isomerases (PPIases):** Promote the isomerization of proline residues, a critical step in protein folding.
* **Protein disulfide isomerases (PDIs):** Facilitate the formation and breakage of disulfide bonds, crucial for the stability of some proteins.

**Proteases:** These enzymes degrade misfolded proteins that cannot be salvaged. They act as a quality control mechanism, removing damaged or improperly folded proteins from the cell. Some important proteases include:

* **Ubiquitin ligases:** Tag misfolded proteins with ubiquitin, marking them for degradation by proteasomes.
* **Proteasomes:** Large protein complexes that break down ubiquitinated proteins into smaller peptides.

**Stress Responses:** When cells are exposed to stress, such as heat shock or oxidative stress, the unfolded protein response (UPR) is activated. This response increases the production of chaperones and folding enzymes, helping to cope with the increased burden of unfolded proteins.

**Overall, the maintenance of unfolded proteins is a dynamic and essential process that ensures the integrity of the proteome. It is a delicate balance between folding, refolding, and degradation, involving a complex network of molecular players. Disruptions in this process can lead to protein aggregation, cellular dysfunction, and disease.**'
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Proteins (1)

Compounds (1)