Ubiquitination
Ubiquitination (pronounced: yoo-bi-kwi-tay-shun) is a post-translational modification process that involves the addition of ubiquitin, a small regulatory protein, to a substrate protein. This process is crucial for various cellular functions, including protein degradation, DNA repair, cell cycle regulation, and immune responses.
Etymology
The term "Ubiquitination" is derived from the protein "Ubiquitin," which is so named because of its ubiquitous presence in all eukaryotic cells.
Process
Ubiquitination involves three main steps: activation, conjugation, and ligation. The Ubiquitin-activating enzyme (E1) activates ubiquitin in an ATP-dependent manner. The activated ubiquitin is then transferred to a Ubiquitin-conjugating enzyme (E2). Finally, a Ubiquitin ligase (E3) catalyzes the transfer of ubiquitin from E2 to the substrate protein.
Functions
Ubiquitination plays a crucial role in several cellular processes:
- Protein degradation: Ubiquitination marks proteins for degradation by the 26S proteasome.
- DNA repair: Ubiquitination regulates the repair of DNA damage.
- Cell cycle regulation: Ubiquitination controls the degradation of cell cycle regulators.
- Immune response: Ubiquitination is involved in the regulation of immune responses.
Related Terms
See Also
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