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Quality control of inclusion bodies in Escherichia coli

Britta Jürgen1, Antje Breitenstein2, Vlada Urlacher3, Knut Büttner4, Hongying Lin5, Michael Hecker4, Thomas Schweder1 and Peter Neubauer67*

Author Affiliations

1 Pharmaceutical Biotechnology, Institute of Pharmacy, Ernst-Moritz-Arndt-Universität, Friedrich-Ludwig-Jahn-Str. 17, D-17487 Greifswald, Germany

2 Scanbec GmbH, Weinbergweg 23, D-06120 Halle/Saale, Germany

3 Institut für Biochemie, Heinrich-Heine-Universität Düsseldorf, Universitätsstr. 1, Bldg. 26.02, D-40225 Düsseldorf, Germany

4 Institute of Microbiology, Ernst-Moritz-Arndt-Universität, Friedrich-Ludwig-Jahn-Str. 15, D-17487 Greifswald, Germany

5 Institut für Biochemie und Molekularbiologie I, Universitätsklinikum Hamburg-Eppendorf, Martinistr. 52, D-20246 Hamburg, Germany

6 Bioprocess Engineering Laboratory, Department of Process and Environmental Engineering and Biocenter Oulu, University of Oulu, FIN-90014 Oulu, Finland

7 Laboratory of Bioprocess Engineering, Department of Biotechnology, Technische Universität Berlin, Ackerstr. 71-76, ACK-24, D-13355 Berlin, Germany

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Microbial Cell Factories 2010, 9:41  doi:10.1186/1475-2859-9-41

Published: 28 May 2010

Abstract

Background

Bacterial inclusion bodies (IBs) are key intermediates for protein production. Their quality affects the refolding yield and further purification. Recent functional and structural studies have revealed that IBs are not dead-end aggregates but undergo dynamic changes, including aggregation, refunctionalization of the protein and proteolysis. Both, aggregation of the folding intermediates and turnover of IBs are influenced by the cellular situation and a number of well-studied chaperones and proteases are included. IBs mostly contain only minor impurities and are relatively homogenous.

Results

IBs of α-glucosidase of Saccharomyces cerevisiae after overproduction in Escherichia coli contain a large amount of (at least 12 different) major product fragments, as revealed by two-dimensional polyacrylamide gel electrophoresis (2D PAGE). Matrix-Assisted-Laser-Desorption/Ionization-Time-Of-Flight Mass-Spectrometry (MALDI-ToF MS) identification showed that these fragments contain either the N- or the C-terminus of the protein, therefore indicate that these IBs are at least partially created by proteolytic action. Expression of α-glucosidase in single knockout mutants for the major proteases ClpP, Lon, OmpT and FtsH which are known to be involved in the heat shock like response to production of recombinant proteins or to the degradation of IB proteins, clpP, lon, ompT, and ftsH did not influence the fragment pattern or the composition of the IBs. The quality of the IBs was also not influenced by the sampling time, cultivation medium (complex and mineral salt medium), production strategy (shake flask, fed-batch fermentation process), production strength (T5-lac or T7 promoter), strain background (K-12 or BL21), or addition of different protease inhibitors during IB preparation.

Conclusions

α-glucosidase is fragmented before aggregation, but neither by proteolytic action on the IBs by the common major proteases, nor during downstream IB preparation. Different fragments co-aggregate in the process of IB formation together with the full-length product. Other intracellular proteases than ClpP or Lon must be responsible for fragmentation. Reaggregation of protease-stable α-glucosidase fragments during in situ disintegration of the existing IBs does not seem to occur.