Reaction Cycle of Chaperonin GroEL via Symmetric “Football” Intermediate

• Symmetrical 1:2 GroEL:GroES2 “football” complex versus asymmetrical 1:1 GroEL:GroES “bullet” complex.
• Substrate protein switches GroEL:GroES from bullet-mediated cycle to football-mediated cycle.
• Crystal structure of the football complexes.

Chaperonin GroEL is an essential chaperone that assists in protein folding in the cell. Since one GroEL ring binds one GroES heptamer, the GroEL double ring permits the formation of two types of GroEL:GroES complexes: asymmetric 1:1 “bullet”-shaped and symmetric 1:2 “football”-shaped GroEL:GroES2 complexes. There have been continuing debates about the mechanism and which complex is critical to the chaperonin-assisted folding. In this review, I summarize the recent progress on the football complex.

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