Download MendeleyFormation and structures of GroEL:GroES2 chaperonin footballs, the protein-folding functional form.
Fei, X., Ye, X., LaRonde, N.A., Lorimer, G.H.(2014) Proc Natl Acad Sci U S A 111: 12775-12780
- PubMed: 25136110
- DOI: https://doi.org/10.1073/pnas.1412922111
- Primary Citation of Related Structures:
4PKN, 4PKO - PubMed Abstract:
The GroE chaperonins assist substrate protein (SP) folding by cycling through several conformational states. With each cycle the SP is, in turn, captured, unfolded, briefly encapsulated (t1/2 ∼ 1 s), and released by the chaperonin complex. The protein-folding functional form is the US-football-shaped GroEL:GroES2 complex. We report structures of two such "football" complexes to ∼ 3.7-Å resolution; one is empty whereas the other contains encapsulated SP in both chambers. Although encapsulated SP is not visible on the electron density map, using calibrated FRET and order-of-addition experiments we show that owing to SP-catalyzed ADP/ATP exchange both chambers of the football complex encapsulate SP efficiently only if the binding of SP precedes that of ATP. The two rings of GroEL thus behave as a parallel processing machine, rather than functioning alternately. Compared with the bullet-shaped GroEL:GroES1 complex, the GroEL:GroES2 football complex differs conformationally at the GroEL-GroES interface and also at the interface between the two GroEL rings. We propose that the electrostatic interactions between the ε-NH(3+) of K105 of helix D in one ring with the negatively charged carboxyl oxygen of A109 at the carboxyl end of helix D of the other ring provide the structural basis for negative inter-ring cooperativity.
Organizational Affiliation:
Biophysics Graduate Program, Center for Biological Structure and Organization.
