Question

An altered version of glycogen synthase is produced in the laboratory, with one of its amino acid residues substituted for another. Unlike normal glycogen synthase, the activity of the mutant protein is unaffected by glycogen synthase kinase-3. Which mutation is MOST likely to produce this effect?

A) Cys -> Ser
B) Ile -> Thr
C) Ser -> Ala
D) Cys -> Met
E) Thr -> Ser

Answer 1

The mutation that is most likely to produce an altered version of glycogen synthase that is unaffected by glycogen synthase kinase-3 is the substitution of Cys (cysteine) with Ser (serine). option A) Cys -> Ser.

Step-by-step explanation:

The mutation that is most likely to produce an altered version of glycogen synthase that is unaffected by glycogen synthase kinase-3 is option A) Cys -> Ser.

In the normal glycogen synthase, glycogen synthase kinase-3 phosphorylates a specific serine residue, which inhibits the activity of glycogen synthase. However, when this serine residue is mutated to a different amino acid, such as serine being substituted with cysteine (Cys), glycogen synthase kinase-3 is unable to phosphorylate it, resulting in the mutant protein being unaffected by glycogen synthase kinase-3.