Programmed Proteolysis by ATP-dependent Protease Complexes
Horst Feldmann*
Adolf-Butenandt-Institut of Munich University, Molecular Biology, Schillerstrasse 44, D-80336 München, Germany
Article history:
Received January 25, 1999
Accepted February 15, 1999
Key words:
proteasomes, energy-dependent proteolysis, ATPases associated activities (AAA) family, proteasome-like complexes
Summary:
Programmed intracellular degradation of proteins is essential for cell survival. In eukaryotic cells, there are two major pathways: (i) Proteolysis of endocytosed proteins such as membrane receptors or extracellular proteins is largely confined to the lysosomal/vacuolar system. (ii) Energy-dependent proteolysis by proteasomes is the major site for the degradation of cellular proteins and plays an important role in many aspects of cellular regulation. Proteasome activity is intimately coupled to the ubiquitin system. More simple proteasomes and proteasome- like complexes have been discovered also in archebacteria and eubacteria. In mitochondria and chloroplasts, a significant part of programmed proteolysis for 'quality control' is achieved by membrane-bound protease complexes. Remarkably, the ATPases in all of these complexes have been found to be members of the ATPase associated activities (AAA) family, which can be considered a specialized subfamily of the ATPase superfamily. This review focuses on the recent advancement of our understanding of the control mechanisms underlying the functions of proteasomes and proteasome-like complexes. Additional systems structurally and functionally related to these complexes are considered briefly.
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