Moreover, it has important regulatory roles in numerous biological processes such as cell cycle, apoptosis or the immune response. The authors report on own data and review the current status of the topic. Protein degradation is a necessity but also a hazard. It must be subject to precise spatial and temporal control to prevent that proteins not destined for degradation are attacked. A basic strategy in controlling protein degradation is compartmentalization, that is sequestration of proteolytic action from the environment.
Many proteases reside within spezialized membrane-surrounded organelles, such as lysosomes.
The advances made in recent years in understanding the structure of the proteasome and its mechanism of action has helped to shape the concept of self-compartmentalization, and the proteasome became its paradigm. 35 different subunits. A smaller particle, the 20S proteasome, forms the core of the proteolytic machinery. First observed in the late sixties in human blood cell and subsequently isolated from numerous eukaryotic organisms, it was, about ten years ago, also found in an archeabacterium, Thermoplasma acidophilum . The recent discovery of 20S proteasomes in a group of bacteria shows that it is in fact an ancestral particle common to all domains of life.