GroEL Ring Separation and Exchange in the Chaperonin Reaction

Cell. 2018 Jan 25;172(3):605-617.e11. doi: 10.1016/j.cell.2017.12.010. Epub 2018 Jan 11.


The bacterial chaperonin GroEL and its cofactor, GroES, form a nano-cage for a single molecule of substrate protein (SP) to fold in isolation. GroEL and GroES undergo an ATP-regulated interaction cycle to close and open the folding cage. GroEL consists of two heptameric rings stacked back to back. Here, we show that GroEL undergoes transient ring separation, resulting in ring exchange between complexes. Ring separation occurs upon ATP-binding to the trans ring of the asymmetric GroEL:7ADP:GroES complex in the presence or absence of SP and is a consequence of inter-ring negative allostery. We find that a GroEL mutant unable to perform ring separation is folding active but populates symmetric GroEL:GroES2 complexes, where both GroEL rings function simultaneously rather than sequentially. As a consequence, SP binding and release from the folding chamber is inefficient, and E. coli growth is impaired. We suggest that transient ring separation is an integral part of the chaperonin mechanism.

Keywords: FCS; FRET; GroEL; GroES; allostery; chaperonin; dcFCCS; dual-color fluorescence cross-correlation spectroscopy; fluorescence correlation spectroscopy; fluorescence resonance energy transfer; protein folding; stopped-flow spectroscopy.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Triphosphate / metabolism
  • Animals
  • Chaperonin 10 / metabolism
  • Chaperonin 60 / chemistry
  • Chaperonin 60 / genetics
  • Chaperonin 60 / metabolism*
  • Mutation
  • Protein Binding


  • Chaperonin 10
  • Chaperonin 60
  • Adenosine Triphosphate