Allostery Model

See Monod (1971) this work also provides accessible and interesting accounts of the allostery and operon models. 

The symmetry model (fig. 2.4) of allostery can describe the cooperative binding of substrate to enzyme (homotropic effect), as well as the influence of effector molecules on the activity of enzymes (heterotropic effect). 

Fig. 2.4. The symmetry model of allostery. Shown here is the succesive binding of a hgand L to a protomer of a tetrameric protein with four ligand-binding sites according to the symmetry model. T tense form, R relaxed form.

Alternative models for hemoglobin allostery, (a) In the symmetry model hemoglobin can exist in only two states. (b) In the sequential model hemoglobin can exist in a number of different states. Only the subunit binding oxygen must be in the high-affinity form. 

Perutz s hypothesis (55) and the MWC model (56) for allostery, that the more tension is added to the tense (deoxy) state of Hb, the greater the shift to the right of the oxygen-... 

Sequential Models Also Can Aeeount for Allosterie Effeets... 

See also Models of Allosteric Activity, Hemoglobin Allostery... 

What major differences exist between the sequential and concerted models for allostery in accounting for hemoglobin that is partially saturated with oxygen ... 

The model of allostery described above can be used to highlight the relationship, or lack thereof, between the observed coupling and any apparent pathway between the linked sites. Shown in Figure 15.5A are the results obtained from the range of stability and interaction parameters used in simulating the allosteric CR of Figure 15.3. 

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 ... 

Allostery and Induced Fit NMR and Molecular Modeling Study of the trp Repressor—mtr DNA... 

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