An expanded conformation of single-ring GroEL-GroES complex encapsulates an 86 kDa substrate

Structure. 2006 Nov;14(11):1711-22. doi: 10.1016/j.str.2006.09.010.


Electron cryomicroscopy reveals an unprecedented conformation of the single-ring mutant of GroEL (SR398) bound to GroES in the presence of Mg-ATP. This conformation exhibits a considerable expansion of the folding cavity, with approximately 80% more volume than the X-ray structure of the equivalent cis cavity in the GroEL-GroES-(ADP)(7) complex. This expanded conformation can encapsulate an 86 kDa heterodimeric (alphabeta) assembly intermediate of mitochondrial branched-chain alpha-ketoacid dehydrogenase, the largest substrate ever observed to be cis encapsulated. The SR398-GroES-Mg-ATP complex is found to exist as a mixture of standard and expanded conformations, regardless of the absence or presence of the substrate. However, the presence of even a small substrate causes a pronounced bias toward the expanded conformation. Encapsulation of the large assembly intermediate is supported by a series of electron cryomicroscopy studies as well as the protection of both alpha and beta subunits of the substrate from tryptic digestion.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Triphosphate / chemistry
  • Chaperonin 10 / chemistry*
  • Chaperonin 60 / chemistry*
  • Cryoelectron Microscopy
  • Crystallography, X-Ray
  • Dimerization
  • Escherichia coli / metabolism*
  • Humans
  • Image Processing, Computer-Assisted
  • Ketone Oxidoreductases / chemistry
  • Models, Molecular
  • Molecular Conformation
  • Mutation
  • Protein Conformation
  • Trypsin / chemistry


  • Chaperonin 10
  • Chaperonin 60
  • Adenosine Triphosphate
  • Ketone Oxidoreductases
  • Trypsin