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