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Questions and Answers
What is the primary role of ubiquitin in protein modification?
What is the primary role of ubiquitin in protein modification?
The primary role of ubiquitin in protein modification is to tag proteins for degradation.
Describe the initial step in the ubiquitination process involving ubiquitin.
Describe the initial step in the ubiquitination process involving ubiquitin.
The initial step involves the activation of ubiquitin by the E1 enzyme, which forms a high-energy thioester bond with ubiquitin using ATP.
What is the role of the E2 enzyme in the ubiquitination process?
What is the role of the E2 enzyme in the ubiquitination process?
The E2 enzyme's role is to transfer the activated ubiquitin from the E1 enzyme to the target protein through the E3 enzyme.
How does the recognition of polyubiquitin chains contribute to protein degradation?
How does the recognition of polyubiquitin chains contribute to protein degradation?
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What happens to ubiquitin molecules after protein degradation?
What happens to ubiquitin molecules after protein degradation?
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Study Notes
Protein Ubiquitination Process
- Ubiquitination is a post-translational modification where a ubiquitin molecule is added to a protein, often marking it for degradation.
- Ubiquitin, a small 76-amino acid protein, is activated by E1 (ubiquitin-activating enzyme).
- E1 forms a high-energy thioester bond between ubiquitin and a cysteine residue using ATP.
- Activated ubiquitin is transferred to E2 (ubiquitin-conjugating enzyme).
- E2 shuttles ubiquitin to E3 (ubiquitin protein ligase).
- E3 attaches ubiquitin to a lysine residue on the target protein.
- Polyubiquitination (multiple ubiquitin molecules attached) is often required for proper degradation tagging.
- Polyubiquitin chains are recognized by the proteasome.
- The proteasome unfolds the protein, moves it to its core, and breaks it down into peptides using ATP.
- Ubiquitin molecules are recycled after protein degradation.
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Description
This quiz explores the intricate process of protein ubiquitination, a vital post-translational modification that signals proteins for degradation. Understand the roles of ubiquitin, E1, E2, and E3 enzymes in this essential cellular process. Test your knowledge on how polyubiquitination and the proteasome function together in protein breakdown.
