Fig. 3: Flexible carboxy termini wobble between the cavity-specific tight (T) and relaxed (R”) conformations.

a Molecular model of asymmetric GroEL-GroES complexes showing filling of the void by CTSs (red space filled). GroEL and GroES are in pale-blue and pink, respectively. One GroEL subunit in each ring is colour-coded to make the change in domain architecture easier to visualise. A, I and E represent apical, intermediate, and equatorial domains, respectively. b Conformational snapshots showing the series of conformations visited by the GroEL heptamer during transition from the T to the R” state. Domains in all the subunits are colour-coded as in (a). Two subunits were removed in the display to reveal the dynamics of CTSs inside the cavity. c Bottom view of the cavity showing the gradual opening of the aperture during the transition, and the dynamic movement of the CTSs. d Cartoon representations of single subunits from the two heptameric rings of GroEL in T and R” conformational states that were subjected to NMA. The rotation and transition of the CTSs are indicated. The helices F, H, I and M are indicated as αF, αH, αI and αM, respectively. e Residue level fluctuations in the torsion angles and displacements of alpha carbon atoms. Fluctuations in the indicated angles and displacements with respect to the T state that were calculated for all seven subunits were averaged and plotted as a function of the primary structure of a subunit. E, I, A, and G represent the regions of GroEL primary structure spanning the corresponding domains as colour-coded in the molecular model. The bold lines mark the regions and are scaled according to the size of the indicated helices.