Allosteric Transitions of Supramolecular Systems Explored by Network Models: Application to Chaperonin GroEL (original) (raw)
Figure 1
GroEL/GroES allosteric cycle.
GroEL consists of two rings, cis and trans, which assume the states: T: ATP-free; R: ATP-bound prior to substrate (peptide) and co-chaperonin (GroES) binding; R′: ATP-, substrate- and GroES-bound; R″: ADP-, substrate- and GroES-bound. Subunits in the T state are shown in red, R in cyan; R′ in green, R″ in blue, and the cap in purple. ATP and ADP are shown by blue and orange boxes. Successive events/reactions along the cycle are (A) binding of seven ATPs to induce the binding of the unfolded substrate (orange), (B) co-chaperonin binding, (C) ATP hydrolysis, (D) ATP binding to trans ring subunits, (E) release of ADPs, substrate (folded or partially folded) and GroES from the cis ring, (F) initiation of a new cycle where the roles of the cis and trans rings are inverted. Top-middle and bottom-left structures are related by rigid body rotation. Diagrams were generated using the data from the PDB in PyMOL (http://www.pymol.org), except for the schematic views of the substrate and ligands included to provide a clearer description. The PDB ids for the structures T/T, R/T, R″/R, R′/T and R″/T are 1GR5, 2C7E and 1GRU [68], 2C7C [15] and 1AON [20], respectively.