Proteasomes and other self-compartmentalizing proteases in prokaryotes.

The proteasome represents the major non-lysosomal proteolytic system in eukaryotes. It confines proteolytic activity to an inner compartment that is accessible to unfolded proteins only. The strategy of controlling intracellular breakdown of proteins by self-compartmentalization is also used by different types of prokaryotic energy-dependent proteases. Genomic sequencing data reveal that various combinations of these energy-dependent proteases occur in prokaryotic cells from different lineages.