Question:medium
This molecule attaches to a protein before its destruction?
This molecule attaches to a protein before its destruction?
Show Hint
Which small protein tags targets for the proteasome in an ATP-dependent way?
Updated On: Jun 24, 2026
- Ubiquitin
- RNAse F
- Zymase
- Chaperone
Show Solution
The Correct Option is A
Solution and Explanation
Step 1: Ask what cells use to label a protein for the proteasome. The signal must be a small protein that is covalently linked to the doomed target.
Step 2: Ubiquitin fits this exactly. In an ATP-dependent reaction, ubiquitin molecules are conjugated to the protein, and a polyubiquitin chain directs it to the 26S proteasome for breakdown.
Step 3: Chaperones help proteins fold correctly, not degrade, while RNase F and zymase have unrelated functions. Therefore the tag attached before destruction is ubiquitin.
\[\boxed{\text{Ubiquitin}}\]
Step 2: Ubiquitin fits this exactly. In an ATP-dependent reaction, ubiquitin molecules are conjugated to the protein, and a polyubiquitin chain directs it to the 26S proteasome for breakdown.
Step 3: Chaperones help proteins fold correctly, not degrade, while RNase F and zymase have unrelated functions. Therefore the tag attached before destruction is ubiquitin.
\[\boxed{\text{Ubiquitin}}\]
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