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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...

The Proteasome

The Proteasome

Eukaryotic cells can degrade proteins through several pathways. One of the most important amongst 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. A series of enzymes carry out the ubiquitination of the target proteins - E1 (ubiquitin-activating enzyme), E2 (ubiquitin-conjugating enzyme), and E3...

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Updated: Apr 11, 2026

Quantifying Subcellular Ubiquitin-proteasome Activity in the Rodent Brain

Quantifying Subcellular Ubiquitin-proteasome Activity in the Rodent Brain

Published on: May 21, 2019

Proteasomes: Isolation and Activity Assays.

Yanjie Li¹, Robert J Tomko^1,2, Mark Hochstrasser¹

¹Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut.

Current Protocols in Cell Biology

|June 11, 2015

Summary

This summary is machine-generated.

Researchers developed a simple purification method for the 26S proteasome and its regulatory (RP) and core (CP) particles from yeast. This enables new assays for ubiquitin-dependent and independent protein degradation.

Keywords:

ATPase proteasome proteolytic activity purification ubiquitin

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Area of Science:

Molecular Biology
Biochemistry
Cell Biology

Background:

The ubiquitin-proteasome system is crucial for protein degradation in eukaryotes.
The 26S proteasome complex, comprising the 19S regulatory particle (RP) and 20S core particle (CP), mediates this process.
Efficient isolation of these complexes is vital for studying their function.

Purpose of the Study:

To establish a straightforward purification protocol for the 26S proteasome, 19S RP, and 20S CP from Saccharomyces cerevisiae.
To develop in vitro assays for assessing both ubiquitin-dependent and ubiquitin-independent proteolytic activities.

Main Methods:

A one-step purification scheme was employed to isolate the proteasome and its subcomplexes from yeast.
Standard biochemical assays were utilized to measure proteolytic activity.

Main Results:

Simple, one-step purification of the 26S proteasome, 19S RP, and 20S CP was achieved.
The study successfully established methods to measure both ubiquitin-dependent and ubiquitin-independent proteolytic activities in vitro.

Conclusions:

The described purification method provides an accessible means to obtain key proteasome components.
The developed assays facilitate the investigation of proteasome function and regulation in protein degradation pathways.