Folding intermediate binds to the bottom of bullet-shaped holo-chaperonin and is readily accessible to antibody

J Mol Biol. 1994 Feb 25;236(3):691-6. doi: 10.1006/jmbi.1994.1181.


Holo-chaperonin from Thermus thermophilus (Thermus holo-cpn) is a bullet-shaped particle where chaperonin-10 heptamer locates at one axial end of the cylindrical body of chaperonin-60 tetradecamer. Thermus holo-cpn promotes in-vitro folding of denatured 3-isopropylmalate dehydrogenase (IPMDH) from the same bacterium. We observed the complexes of Thermus holo-cpn and folding intermediates of IPMDH by immuno-electron microscopy after decoration by single layer labeling with anti-IPMDH IgG or by double layer labeling with anti-IPMDH IgG as first layer and antibodies against IgG as second layer. Images of the electron microscope showed that anti-IPMDH IgG was bound to the bottom end of the bullet-shaped Thermus holo-cpn. This result provides direct evidence that the folding intermediate binds to the axial end, which is opposite to the end where chaperonin-10 heptamer resides, of the cylindrical body of chaperonin-60 tetradecamer, and that bound folding intermediate in the complex is sufficiently exposed to the outside to be accessible by antibody.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 3-Isopropylmalate Dehydrogenase
  • Alcohol Oxidoreductases / chemistry*
  • Alcohol Oxidoreductases / metabolism
  • Alcohol Oxidoreductases / ultrastructure
  • Antibodies
  • Bacterial Proteins / chemistry
  • Bacterial Proteins / metabolism
  • Binding Sites, Antibody
  • Chaperonin 10
  • Chromatography, Gel
  • Heat-Shock Proteins / chemistry*
  • Heat-Shock Proteins / metabolism
  • Immunoglobulin G
  • Microscopy, Immunoelectron
  • Protein Folding*
  • Thermus thermophilus / enzymology
  • Thermus thermophilus / metabolism*


  • Antibodies
  • Bacterial Proteins
  • Chaperonin 10
  • Heat-Shock Proteins
  • Immunoglobulin G
  • Alcohol Oxidoreductases
  • 3-Isopropylmalate Dehydrogenase