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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...

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...

The Proteasome

The Proteasome

Protein Complexes with Interchangeable Parts

Protein Complexes with Interchangeable Parts

Groups of proteins may form a complex where each protein in this complex has a different role in the overall execution of the complex’s function. Often some of the proteins in the complex can be replaced by a closely related variant to give a complex that contains many of the same components yet is functionally distinct.
The SCF ubiquitin ligase is a protein complex of five individual proteins. This complex attaches ubiquitin to other target proteins to mark them for degradation. In order...

Conservation of Protein Domains Over Different Proteins

Conservation of Protein Domains Over Different Proteins

Protein domains are small structurally independent units that are part of a single amino acid chain. Although these domains are often structurally independent, they may rely on synergistic effects to perform their functions as part of a larger protein. Protein domains may be conserved within the same organism, as well as across different organisms.
A limited set of protein domains often duplicate and recombine during evolution. These domains can be organized in different combinations to...

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Related Experiment Video

Updated: Mar 28, 2026

Quantifying Subcellular Ubiquitin-proteasome Activity in the Rodent Brain

Quantifying Subcellular Ubiquitin-proteasome Activity in the Rodent Brain

Published on: May 21, 2019

Mammalian proteasome subtypes: Their diversity in structure and function.

Burkhardt Dahlmann¹

¹Institute of Biochemistry, Charité - Universitätsmedizin Berlin CCO, Charitéplatz 1, 10117 Berlin, Germany.

Archives of Biochemistry and Biophysics

|January 3, 2016

Summary

This summary is machine-generated.

The 20S proteasome, a key protein degrader, exists in various subtypes in mammalian cells. Understanding these proteasome subtypes is crucial for their biological and medical applications.

Keywords:

Posttranslational modification Proteasome Subpopulation Subtype Subunit-iso/proteoform

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Cell Subtype-specific Analysis of Neuronal Membrane Proteasome in Somatosensory Neurons

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Area of Science:

Cell Biology
Biochemistry
Molecular Biology

Background:

The 20S proteasome is a central multicatalytic proteinase responsible for degrading most intracellular proteins.
It plays a vital role in fundamental cellular processes and associates with regulatory complexes, forming structures like the 26S proteasome.
The 20S proteasome's core structure consists of four stacked rings made of α- and β-subunits.

Purpose of the Study:

To review current knowledge on proteasome subtypes in mammalian cells and tissues.
To explore the potential biological and medical relevance of these diverse proteasome subtypes.

Main Methods:

Literature review of existing research on proteasome structure and function.
Analysis of proteasome subpopulations (standard, immuno-, intermediate) based on β-subunit composition.
Consideration of posttranslational modifications and genetic variations leading to iso- and proteoforms.

Main Results:

Three main proteasome subpopulations exist: standard, immuno-, and intermediate proteasomes.
The presence of multiple iso- or proteoforms for α- and β-subunits results in numerous 20S proteasome subtypes within each subpopulation.
Mammalian cells exhibit a wide variety of 20S proteasome subtypes.

Conclusions:

The diversity of 20S proteasome subtypes in mammalian systems is significant.
Further research into these subtypes may reveal important biological functions and therapeutic targets.