Folding of a misfolding-prone β-galactosidase in absence of DnaK

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In absence of chaperone DnaK, bacterially produced misfolding-prone proteins aggregate into large inclusion bodies, but still a significant part of these polypeptides remains in the soluble cell fraction. The functional analysis of the model β-galactosidase fusion protein VP1LAC produced in DnaK - cells has revealed that the soluble version exhibits important folding defects and that it is less stable and less active than when produced in wild-type DnaK+ cells. In addition, we have observed that the induction of gene expression at the very late exponential phase enhances twofold the stability of VP1LAC, a fact that in DnaK- background results in a dramatic increase of its specific activity up to phenotypically detectable levels. These results indicate that the chaperone DnaK is critical for the folding of misfolding-prone proteins and also that the soluble form reached in its absence by a fraction of polypeptides is not necessarily supportive of biological activity. In the case of E. coli β-galactosidase, the catalytic activity requires assembling into tetramers and the fine organization of the activating interfaces holding the active sites, what might not be properly reached in absence of DnaK. © 2005 Wiley Periodicals, Inc.
Original languageEnglish
Pages (from-to)869-875
JournalBiotechnology and Bioengineering
Issue number7
Publication statusPublished - 30 Jun 2005


  • Aggregation
  • Chaperones
  • DnaK
  • Heat-shock
  • Protein folding
  • Recombinant protein


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