The smooth and efficient functioning of any system necessarily requires a mechanism for recognizing and removing components that have served their purpose and are no longer needed, in order to make way for ones that are. It's waste disposal, and at the cellular level it's the important activity of proteasomes that maintain cellular health by identifying and degrading proteins that have been targeted as obsolete or damaged. (To put this in perspective, consider that at any given moment a human cell typically contains about 100,000 different proteins.) This housekeeping function of proteasomes is critical to a broad range of vital biochemical processes, including transcription, DNA repair, and the immune defense system. Since the proteasome process was only first described in 2004 (by Nobel Prize-winning chemists), our understanding of its mechanics has been limited.