Two Ligands, a and B, Bind to Two Different Conformations

question 10

Multiple Choice

Two ligands, A and B, bind to two different conformations of the enzyme X. The ligand A is the enzyme's substrate, whereas ligand B binds to a remote allosteric site. Which of the following is a consequence of this arrangement?

• A) Binding of A to X does not affect the affinity of X for binding to B.
• B) Binding of B to X does not affect the rate of reaction catalyzed by X.
• C) Binding of A to X increases the affinity of X for B.
• D) Binding of B to X decreases the affinity of X for A.
• E) Binding of B to X has a large effect on the binding of A to X, but binding of A to X has a small effect on X-B binding.