What type of amino acid tag is recognized by protease for degrading a protein?

The type of amino acid tag that is recognized by proteases for directing the degradation of a protein is ubiquitin. Ubiquitin is a small protein that is covalently attached to target proteins in a process called ubiquitination. This modification signals that the tagged protein should be delivered to the proteasome, a large protein complex responsible for breaking down unneeded or damaged proteins into smaller peptides.

Ubiquitination plays a critical role in regulating many cellular processes, including the cell cycle and response to stress. It serves as a signal for the protein to be recognized and processed by the proteolytic machinery of the cell, leading to protein degradation. While start and stop codons are crucial for initiating and terminating protein synthesis, they do not play a role in marking proteins for degradation. Similarly, signal peptides direct proteins to specific cellular locations but are not involved in signaling for degradation.