Construction and deconstruction of bacterial inclusion bodies.

Bacterial inclusion bodies (IBs) are refractile aggregates of protease-resistant misfolded protein that often occur in recombinant bacteria upon gratuitous overexpression of cloned genes. In biotechnology, the formation of IBs represents a main obstacle for protein production since even favouring high protein yields, the in vitro recovery of functional protein from insoluble deposits depends on technically diverse and often complex re-folding procedures. On the other hand, IBs represent an exciting model to approach the in vivo analysis of protein folding and to explore aggregation dynamics. Recent findings on the molecular organisation of embodied polypeptides and on the kinetics of inclusion body formation have revealed an unexpected dynamism of these protein aggregates, from which polypeptides are steadily released in living cells to be further refolded or degraded. The close connection between in vivo protein folding, aggregation, solubilisation and proteolytic digestion offers an integrated view of the bacterial protein quality control system of which IBs might be an important component especially in recombinant bacteria.