Final answer:
The 20S core particle of the proteasome is the protein quality control factor that is not ATP-dependent and acts as a protease, capable of degrading proteins into amino acids without the need for ATP.
Step-by-step explanation:
The only known protein quality control factor that isn't ATP-dependent and functions as a protease is the 20S core particle of the proteasome. This component of the proteasome system degrades proteins in a process that does not require ATP. It's notable because most protein degradation pathways, such as those involving the ubiquitin-proteasome system, require ATP for tagging proteins with ubiquitin or for unfolding proteins so they can enter the proteasome. The 20S proteasome has proteolytic active sites that are sequestered within an internal chamber, allowing for the degradation of peptides into smaller amino acids, a process that is ATP-independent.