The proteasome is the central enzyme of the ATP-ubiquitin-dependent proteolytic pathway. It is responsible for the elimination of abnormal proteins, arising from mutations or damage ensuing from adverse external conditions. Moreover, it has important regulatory roles in numerous biological processes such as cell cycle, apoptosis or the immune response. A research team at the Max Planck Institute of Biochemistry in Martinsried/Germany, headed by Wolfgang Baumeister, since several years one of the leading groups in the proteasome field, has published a review-article in Cell on February 6, 1998, reflecting on the proteasome as one of the most fascinating macromolecular machines of the cell. 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. Another mechanism of control, which offers greater logistic flexibility, is self- or autocompartmentalization: proteolytic subunits self-associate into barrel-shaped complexes with inner cavities that harbour the active sites. 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.

The molecular species that functions in the ubiquitin-proteasome pathway is the so-called 26S proteasome, a large complex composed of approx. 35 different subunits. A smaller particle, the 20S
'"/>

Contact: Erika Seemller
seemuell@biochem.mpg.de
+49-89-8578-2634
Max-Planck-Gesellschaft
2-Mar-1998