Question

Proteasomes are hollow, cylindrical, protein-degrading machines found in both the cytosol and the nucleus of cells. Proteins that are to be degraded by proteasomes are labeled by ________.

Answer 1

Proteins are targeted for degradation in proteasomes by being labeled with ubiquitin, which signals the protein's end of life, leading to its digestion into amino acids.

Step-by-step explanation:

Proteins that are to be degraded by proteasomes are labeled by ubiquitin. This small protein attaches to the target protein to be degraded, signaling its end of life span. Ubiquitin essentially flags the protein for destruction and directs it to the proteasome, a protein-degrading complex.

Within the proteasome, the protein is unfolded and digested into short peptide fragments by proteolytic enzymes. Finally, these fragments are released into the cytoplasm, where they are broken down to free amino acids.