In Humans, Nearly 80% of Proteins Are Acetylated on Their

Multiple Choice

In humans, nearly 80% of proteins are acetylated on their N-terminal residue, a modification known to be recognized by a specific E3 enzyme, which directs the ubiquitylation of the protein for rapid degradation. Does this mean that all of these proteins are actively degraded at any given time?

A) Yes; this high turnover rate ensures that their activity is under tight control.
B) Yes; but they are not fully degraded in this way and can still function as protein fragments.
C) No; the destruction signal can be buried in the interior of the protein or bound to other proteins.
D) No; the E3 enzyme recognizing this mark is inactive most of the time.