Question

A pharmaceutical research group is studying the allosteric regulation mechanisms for an enzyme involved in kidney cancer. They perform a number of different assays and make the following observations. Using these observations, determine whether the model is most consistent with

a. induced-fit/sequential

b. MWC/symmetry

c. both models

Observations:

-the enzyme's allostertic activator binds to an allosteric site located 1.5 nanometers away from the active site.

-when the allosteric activator binds to the allosteric site, NMR signals indicate that a significiant conformational change takes place in the active site

- when the allosteric activator dissociates from the allosteric site, the active site returns to its original conformation

-NMR data indicate that there is no equilibrium between different conformations of the enzyme in teh absence of allosteric activator

i.  

Answer 1

According to MWC or concerted or symmetry model enzymes substrate binding site are linked in such a way that the conformational changes in one subunit upon binding of the substrate or regulatory molecules bring the conformational changes in another subunit of the enzyme and thus all subunit must exist in the same conformation. this fact is justified by the above-given example stating that binding allosteric activator at the allosteric site causes conformational changes in the active site and same on the dissociation of activator molecule.

on the other hand, induce fit model illustrate that conformational changes occur only in an active site in order to enhance the binding of substrate to the active site and binding of substrate to the active site does not change the conformation of any other site of the enzyme. So the above-given case is an example of an MWC/symmetry model.