In vivo observation of polypeptide flux through the bacterial chaperonin system

Cell. 1997 Aug 8;90(3):491-500. doi: 10.1016/s0092-8674(00)80509-7.


The quantitative contribution of chaperonin GroEL to protein folding in E. coli was analyzed. A diverse set of newly synthesized polypeptides, predominantly between 10-55 kDa, interacts with GroEL, accounting for 10%-15% of all cytoplasmic protein under normal growth conditions, and for 30% or more upon exposure to heat stress. Most proteins leave GroEL rapidly within 10-30 s. We distinguish three classes of substrate proteins: (I) proteins with a chaperonin-independent folding pathway; (II) proteins, more than 50% of total, with an intermediate chaperonin dependence for which normally only a small fraction transits GroEL; and (III) a set of highly chaperonin-dependent proteins, many of which dissociate slowly from GroEL and probably require sequestration of aggregation-sensitive intermediates within the GroEL cavity for successful folding.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacterial Proteins / biosynthesis*
  • Bacterial Proteins / chemistry*
  • Chaperonin 60 / metabolism*
  • Chaperonins / metabolism*
  • Chloramphenicol O-Acetyltransferase / biosynthesis
  • Chloramphenicol O-Acetyltransferase / chemistry
  • Escherichia coli / metabolism*
  • Kinetics
  • Models, Structural
  • Plasmids
  • Protein Biosynthesis
  • Protein Folding*
  • Recombinant Proteins / biosynthesis
  • Recombinant Proteins / chemistry
  • Thiosulfate Sulfurtransferase / biosynthesis
  • Thiosulfate Sulfurtransferase / chemistry
  • beta-Lactamases / biosynthesis
  • beta-Lactamases / chemistry


  • Bacterial Proteins
  • Chaperonin 60
  • Recombinant Proteins
  • Chloramphenicol O-Acetyltransferase
  • Thiosulfate Sulfurtransferase
  • beta-Lactamases
  • Chaperonins