Evolutionary steps towards complex proteolytic machineries

Controlled protein degradation plays a crucial role for the correct progression of cell cycle, signal transduction, gene expression or programmed cell death. In eukaryotes, organisms with a nucleus, a complex machinery of enzymes handles this highly regulated process. Recently, the existence of related enzyme systems has also been found in prokaryotes, organisms without a nucleus. The analysis of these nanomachines provides insight into the evolution of cellular protein degradation and the origin of the eukaryotic degradation machinery.