The Escherichia coli DnaK chaperone stimulates the α-complementation of β-galactosidase

Samuel Berhanu, Takuya Ueda, Jean Hervé Alix*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


pUC18 and pUC19 are well-known high copy-number plasmid vectors routinely used for DNA cloning purposes. We show here that, in Escherichia coli transformed by native pUC18, the α-complementation of β-galactosidase (i.e., mediated by the peptide LacZα18) is intrinsically weak and slow, but is greatly stimulated by the DnaK/DnaJ/GrpE chaperone system. In contrast, the α-complementation mediated by the peptide LacZα19 (in E. coli transformed by the native pUC19) is much more efficient and therefore does not require the assistance of the DnaK chaperone machinery. The marked difference between these two LacZα peptides is reproduced in a cell-free protein expression system coupled with α-complementation. We conclude that: (i) α-complementation of β-galactosidase is DnaK-mediated depending upon the LacZα peptide donor; (ii) DnaK, sensu stricto, is not necessary for α-complementation, but can enhance it to a great extent; (iii) this observation could be used to establish an easy and inexpensive method for screening small molecules libraries in search of DnaK inhibitors and also for deciphering the DnaK-mediated protein quality control mechanism.

Original languageEnglish
Pages (from-to)669-688
Number of pages20
JournalJournal of Basic Microbiology
Issue number6
Publication statusPublished - 2022 Jun
Externally publishedYes


  • chaperone DnaK
  • plasmids pUC18/pUC19
  • α-complementation
  • β-galactosidase

ASJC Scopus subject areas

  • Applied Microbiology and Biotechnology


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