Figure A shows a protein consisting of two identical subunits. Figure B shows th

Question

Figure A shows a protein consisting of two identical subunits. Figure B shows the same protein after each subunit has been covalently modified with a phosphate group. Based on the activities shown in the diagrams, what biological advantage does this protein gain by having the ability to undergo a reversible phosphorylation–dephosphorylation reaction? a. It gains the ability to resist denaturation. b. It gains the ability to undergo reversible subunit dissociation. c. It gains a mechanism for regulating substrate binding. d. It gains a broader range of molecules that will bind to its binding sites. e. It gains a broader range of biological functions that it can carry out.

Explanation / Answer

Answer: (c) It gains a mechanism for regulating substrate binding.

Explanation:

From the given figures, it is clear that the phosphorylation event results in a conformational change in the ligand binding pocket of the protein. This facilitates the binding of the ligand to the phosphorylated protein.

Dephosphosphorylation of the protein would result in a conformational switch to its inactive state (a change in the conformation of the ligand binding cleft) such that the ligand can no longer bind to the dephosphorylated protein.

Thus, this reversible phosphorylation and dephosphorylation event imparts the protein the ability to regulate substrate binding.

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