What is the role of ubiquitin in protein metabolism?

A It acts as an enzyme to break down proteins
B It marks proteins for degradation by the proteasome ✓
C It inhibits protein synthesis
D It stimulates protein folding

Explanation

Ubiquitin is a small protein that marks other proteins for degradation by the proteasome, a process known as ubiquitination.

Source

Alberts et al., Molecular Biology of the Cell
Protein Metabolism Biochemistry Protein Degradation Medium NURSING Confidence: high