Conformational changes induced by ligand binding

Thus if Ul= Uh, independently of the other parameters of the system (Ea and Eap), there is no indirect correlation. This result means that the indirect correlation is intimately connected with the conformational changes induced by the binding of the ligand. If Ul = Uh, there is no effect of G on the equilibrium composition of the L and H forms. This result is essentially the same as in the model treated in section 3.2.3 [see Eq. (3.2.31)]. 

We see that if 77 = 1 then, although there exists a conformational change induced by the binding, this effect is not communicated between the two subunits. We have already seen that T] = 1 leads to independence of the subunits [see Eq. (3.3.12)], which means that conformational changes induced by the binding process affects only the subunit on which the ligand binds. This is therefore the same as in the model of section 2.10. 

Numerous experimental and theoretical studies have documented the direct correlation between internal motions of an enzyme and its activity. For example, the catalytic activities of many enzymes are closely associated with loop motions, which open and close the active site and also position key residues into contact with the substrate [7, 8]. X-ray crystal structmes of hgand-bound and fi-ee enzymes show that substantial conformational changes can be induced by ligand binding and by chemical transformation during an enzymatic reaction [9, 10]. The reaction catalyzed by thymidylate synthase has been shown to couple directly with the protein s conformation-... 

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