Allosteric control Monod-Wyman-Changeux model

The mammalian (largely rabbit) muscle enzyme has been the most investigated X-ray structural work favours a GTB fold. It has control, covalent and allosteric, at several levels and these are usually discussed in terms of a modification of the Monod-Wyman-Changeux model, in which the individual polypeptide monomers can adopt either a non-catalytic T ( tense ) state or a catalytic R ( relaxed ) state, but mixed oligomers (e.g. TR in a dimer) do not occur. In the extensive structural studies, oligomers with mixed conformations have never been observed. 

As discussed in Section 15.1, numerous protein systems have been observed to behave in a manner consistent with a structural-mechanical basis of allosteric control between coupled sites, in which the sites are connected structurally by a network of interactions or pathways [14,15]. In these systems, allostery typically has been presented in terms of the Monod-Wyman-Changeux (MWC) [8] and Koshland-Nemethy-Filmer (KNF) [9] models, both of which are special cases of a more general model [61]. Briefly, the MWC model describes allostery as originating from the equilibria between two macroscopic states, each of which can bind ligand with different affinities. In this model, the equilibrium is driven toward the high-affinity state by mass action. The KNF model, however, relies on an induced fit ... 

---