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Updated: Aug 8, 2026
11:36
In Vitro Ubiquitination and Deubiquitination Assays of Nucleosomal Histones
Published on: July 25, 2019
Synthetic signals for ubiquitin-dependent proteolysis
1Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115, USA.
Molecular and Cellular Biology
|August 1, 1995
Summary
Researchers identified three classes of protein degradation signals. These signals, crucial for short-lived protein turnover, involve specific ubiquitin-conjugating enzymes and structural features like amphipathic helices and hydrophobic residues.
Area of Science:
- Molecular Biology
- Proteomics
- Biochemistry
Background:
- Short-lived proteins require degradation signals for turnover.
- Structural features of these degradation signals are not well understood.
Purpose of the Study:
- To isolate and characterize novel protein degradation signals.
- To define the structural and enzymatic requirements for signal recognition.
Main Methods:
- Screening artificial sequences for reporter protein destabilization.
- Analyzing protein turnover in yeast mutants lacking specific ubiquitin-conjugating enzymes (Ubc) and ubiquitin protein ligase (Ubr1).
- Investigating the role of amino acid substitutions in signal recognition.
Main Results:
- Identified three classes of degradation signals (Class I, II, III).
- Class I signals promote N-terminal processing via Ubc2 and Ubr1.
- Class II signals require Ubc6, Ubc7, Ubc4/Ubc5 and appear as amphipathic alpha-helices.
- Class III signals involve hydrophobic residues and Ubc4/Ubc5.
Conclusions:
- Degradation signals have diverse structural and enzymatic requirements.
- Hydrophobic residue clusters are critical for Class II and III signal recognition.
- Novel pathways for protein degradation based on the N-end rule were defined.
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02:04Covalently 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.
These groups modify specific amino acids in a protein.
02:18The 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...
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...
02:58Regulated 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...
Protein degradation plays two important roles in the cells. It helps to protect cells from misfolded or damaged proteins before they lead to a...
02:18The 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...
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...
02:58Regulated 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...
Protein degradation plays two important roles in the cells. It helps to protect cells from misfolded or damaged proteins before they lead to a...
01:13The 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 (ubiquitin...
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 (ubiquitin...