Polypeptide flux through bacterial Hsp70: DnaK cooperates with trigger factor in chaperoning nascent chains

Cell. 1999 Jun 11;97(6):755-65. doi: 10.1016/s0092-8674(00)80787-4.


A role for DnaK, the major E. coli Hsp70, in chaperoning de novo protein folding has remained elusive. Here we show that under nonstress conditions DnaK transiently associates with a wide variety of nascent and newly synthesized polypeptides, with a preference for chains larger than 30 kDa. Deletion of the nonessential gene encoding trigger factor, a ribosome-associated chaperone, results in a doubling of the fraction of nascent polypeptides interacting with DnaK. Combined deletion of the trigger factor and DnaK genes is lethal under normal growth conditions. These findings indicate important, partially overlapping functions of DnaK and trigger factor in de novo protein folding and explain why the loss of either chaperone can be tolerated by E. coli.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism*
  • Chaperonin 60 / metabolism
  • Cyclophilins*
  • Escherichia coli / genetics
  • Escherichia coli / metabolism
  • Escherichia coli Proteins*
  • Genes, Bacterial
  • HSP70 Heat-Shock Proteins / genetics
  • HSP70 Heat-Shock Proteins / metabolism*
  • Peptides / metabolism*
  • Peptidylprolyl Isomerase / genetics
  • Peptidylprolyl Isomerase / metabolism*
  • Protein Folding
  • Ribosomes / metabolism


  • Bacterial Proteins
  • Chaperonin 60
  • Escherichia coli Proteins
  • HSP70 Heat-Shock Proteins
  • Peptides
  • dnaK protein, E coli
  • Cyclophilins
  • PPIE protein, human
  • Peptidylprolyl Isomerase