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Regulated Protein Degradation

Regulated Protein Degradation

It is vital to regulate the activity of enzymatic as well as non-enzymatic proteins inside the cell. This can be achieved either through creating a balance between their rate of synthesis and degradation or regulating the intrinsic activity of the protein. Both these regulation mechanisms play an essential role in the normal functioning of cells.
Protein degradation plays two important roles in the cells. It helps to protect cells from misfolded or damaged proteins before they lead to a...

The Proteasome

The Proteasome

Eukaryotic cells can degrade proteins through several pathways. One of the most important among these is the ubiquitin-proteasome pathway. It helps the cell eliminate the misfolded, damaged, or unwarranted cytoplasmic proteins in a highly specific manner.
In this pathway, the target proteins are first tagged with small proteins called ubiquitin. This involves participation of a series of enzymes including— E1 (ubiquitin-activating enzyme), E2 (ubiquitin-conjugating enzyme), and E3...

Tagging and Fusion Proteins

Tagging and Fusion Proteins

Proteins are involved in several cellular processes and biochemical reactions. Analyzing a specific protein of interest requires it to be isolated from the other proteins in the cell. This is achieved by overexpressing the specific gene in a suitable host to produce large quantities of the target protein. A tag or label is recombined with the gene to produce a fusion protein containing the target protein and the tag. The tags on these fusion proteins can then be used for easy detection and...

Covalently Linked Protein Regulators

Covalently Linked Protein Regulators

Proteins can undergo many types of post-translational modifications, often in response to changes in their environment. These modifications play an important role in the function and stability of these proteins. Covalently linked molecules include functional groups, such as methyl, acetyl, and phosphate groups, and also small proteins, such as ubiquitin. There are around 200 different types of covalent regulators that have been identified.
These groups modify specific amino acids in a protein....

The Proteasome Structure

The Proteasome Structure

The ubiquitin-proteasome pathway is a well-known mechanism utilized by eukaryotic cells to remove cytoplasmic proteins that are misfolded, damaged, or no longer needed. In this pathway, the protein that needs to be eliminated undergoes a process called ubiquitination, where a chain of ubiquitin molecules is attached to the 48th lysine residue of the target protein. This ubiquitin modification helps the proteasome distinguish between a target protein and a healthy protein.
The proteasome is an...

Export of Misfolded Proteins out of the ER

Export of Misfolded Proteins out of the ER

After folding, the ER assesses the quality of secretory and membrane proteins. The correctly folded proteins are cleared by the calnexin cycle for transport to their final destination, while misfolded proteins are held back in the ER lumen. The ER chaperones attempt to unfold and refold the misfolded proteins but sometimes fail to achieve the correct native conformation. Such terminally misfolded proteins are then exported to the cytosol by ER-associated degradation or ERAD pathway for...

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Related Experiment Video

Updated: Oct 1, 2025

In Vitro Ubiquitination and Deubiquitination Assays of Nucleosomal Histones

In Vitro Ubiquitination and Deubiquitination Assays of Nucleosomal Histones

Published on: July 25, 2019

Site-specific ubiquitination: Deconstructing the degradation tag.

Emma C Carroll¹, Susan Marqusee²

¹Institute for Neurodegenerative Diseases, University of California, San Francisco, San Francisco, CA, 94038, USA.

Current Opinion in Structural Biology

|March 5, 2022

Summary

Ubiquitin tagging regulates protein fate, determining whether proteins are degraded or not. Site-specific ubiquitin modifications are key to understanding these distinct cellular outcomes and developing new therapeutics.

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Last Updated: Oct 1, 2025

In Vitro Ubiquitination and Deubiquitination Assays of Nucleosomal Histones

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Profiling Ubiquitin and Ubiquitin-like Dependent Post-translational Modifications and Identification of Significant Alterations

Profiling Ubiquitin and Ubiquitin-like Dependent Post-translational Modifications and Identification of Significant Alterations

Published on: November 7, 2019

Area of Science:

Molecular Biology
Cell Biology
Biochemistry

Background:

Ubiquitin, a key posttranslational modification (PTM), tags proteins for degradation by the 26S proteasome.
Ubiquitination also regulates numerous non-degradative cellular processes, highlighting its versatility.
Distinguishing between degradative and non-degradative ubiquitination remains a challenge.

Purpose of the Study:

To explore how site-specificity in ubiquitination influences protein fate and cellular outcomes.
To emphasize the role of ubiquitination site specificity in regulating proteasomal degradation.
To discuss recent advances in understanding ubiquitination's impact on protein dynamics.

Main Methods:

Review of recent advances in structural biology.
Integration of biophysical and cell biology findings.
Analysis of ubiquitination site specificity mechanisms.

Main Results:

Site-specific ubiquitination precisely modulates distinct protein fates.
Understanding site specificity is crucial for deciphering degradative versus non-degradative pathways.
Ubiquitination alters target protein dynamics.

Conclusions:

Recent advances clarify how ubiquitination site specificity dictates protein fate.
This knowledge has implications for designing targeted protein degradation therapeutics.
Further research in structural biology, biophysics, and cell biology is essential.