Biological role of bacterial inclusion bodies: A model for amyloid aggregation

Inclusion bodies are insoluble protein aggregates usually found in recombinant bacteria when they are forced to produce heterologous protein species. These particles are formed by polypeptides that cross-interact through sterospecific contacts and that are steadily deposited in either the cell's cytoplasm or the periplasm. An important fraction of eukaryotic proteins form inclusion bodies in bacteria, which has posed major problems in the development of the biotechnology industry. Over the last decade, the fine dissection of the quality control system in bacteria and the recognition of the amyloid-like architecture of inclusion bodies have provided dramatic insights on the dynamic biology of these aggregates. We discuss here the relevant aspects, in the interface between cell physiology and structural biology, which make inclusion bodies unique models for the study of protein aggregation, amyloid formation and prion biology in a physiologically relevant background. Many eukaryotic polypeptides form inclusion bodies when producedin bacteria. The dissection of the quality control machinery in bacteria and the discovery of the amyloid-like nature of bacterial aggregates have provided an excitingand new view on their dynamic biology, suggesting thatthey may serve as models to study the mechanisms of amyloid aggregation in physiologically relevant conditions. © 2011 The Authors Journal compilation © 2011 FEBS.