Comparison of eucaryal 26S proteasome to the ClpAP protease of eubacteria. The self-compartmentalized proteolytic chambers (20S proteasome, ClpP protease) require an energy-dependent component of the AAA+ ATPase superfamily (19S cap, ClpA ATPase) for degradation of substrate proteins. The 19S cap can be subdivided into two components. The lid domain is involved in recognition of ubiquitin-labeled substrates. The base domain is composed of eight subunits including six AAA ATPases. These ATPases are predicted to form a ring-like structure similar to ClpA and function in unfolding substrates in an energy-dependent mechanism for degradation by the proteasome. The archaeal PAN protein appears to function in unfolding substrate proteins similar to this 26S proteasome ATPase ring and Clp ATPases of eubacteria.
Figure
adapted with permission from S. Wickner, M.R. Maurizi, and S. Gottesman.
Department of Microbiology and
Cell Science
University of Florida
Gainesville, FL 32611-0700