Journal of Biotechnology 125 (2006) 110–113 Short communication Protein activity in bacterial inclusion bodies correlates with predicted aggregation rates Natalia S´ anchez de Groot, Salvador Ventura * Departament de Bioqu´ ımica i Biologia Molecular, Institut de Biotecnologia i de Biomedicina, Universitat Aut` onoma de Barcelona, E-08193 Bellaterra, Spain Received 14 December 2005; received in revised form 8 February 2006; accepted 14 February 2006 Abstract Recent data show that protein aggregation as bacterial inclusion bodies does not necessarily imply loss of biological activity. Here, we investigate the effect of a large set of single-point mutants of an aggregation-prone protein on its specific activity once deposited in inclusion bodies. The activity of such aggregates significantly correlates with the predicted aggregation rates for each mutant, suggesting that rationally tuning the kinetic competition between folding and aggregation might result in highly active, inclusion bodies. The exploration of this technology during recombinant protein production would have a significant biotechnological value. © 2006 Elsevier B.V. All rights reserved. Keywords: Inclusion bodies; Recombinant protein expression; Protein aggregation; Protein folding; Escherichia coli Protein misfolding is a common event during bacte- rial over-expression of recombinant genes (Baneyx and Mujacic, 2004). The aggregation of insoluble polypep- tide chains as inclusion bodies (IBs) is the main bottle- neck in protein production, narrowing the spectrum of relevant polypeptides obtained by recombinant tech- niques and hampering the development of top pri- ority research areas such as the de novo design of novel proteins, the rational modification of natural pro- teins and structural genomics and proteomics. Being * Corresponding author. Tel.: +34 93581 4147; fax: +34 93581 1264. E-mail address: salvador.ventura@uab.es (S. Ventura). widespreadly believed that IB proteins are biologically inert and therefore useless in bioprocesses, many bio- logically relevant proteins have been disregarded for commercialisation. We have shown recently that not only the aggre- gation of different recombinant proteins as bacterial IBs does not necessarily inactivate them but also that active IBs can be used in suspension as efficient cat- alysts for bioprocesses (Garcia-Fruitos et al., 2005). In concrete, the over-expression of a fusion of the aggregation-prone, Alzheimer-related peptide A42 to green fluorescent protein (GFP) resulted in highly fluo- rescent IBs. In the present study, we have quantitatively investigated the biological activity of the IBs formed 0168-1656/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.jbiotec.2006.02.026