The allosteric mechanism of the chaperonin GroEL: a dynamic analysis.

Normal mode calculations on individual subunits and a multisubunit construct are used to analyze the structural transitions that occur during the GroEL cycle. The normal modes demonstrate that the specific displacements of the domains (hinge bending, twisting) observed in the structural studies arise from the intrinsic flexibility of the subunits. The allosteric mechanism (positive cooperativity within a ring, negative cooperativity between rings) is shown to be based on coupled tertiary structural changes, rather than the quaternary transition found in classic allosteric proteins. The results unify static structural data from x-ray crystallography and cryoelectron microscopy with functional measurements of binding and cooperativity.