A Research Group Discovers That a Reagent Can Be Used

Multiple Choice

A research group discovers that a reagent can be used to form covalent cross-links between various types of atoms in both small molecules and proteins.They add the reagent to a mixture of ¹⁴C-lactose and a protein that is thought to have a specific binding site for lactose.What should they do next to draw a conclusion about whether the protein specifically binds lactose?

A) Determine whether any radiolabel becomes covalently linked to protein, and repeat the experiment under high concentrations of urea to see if the sites of radiolabel linkage to the protein change.
B) Denature the protein and observe whether radiolabel is released, and then repeat the experiment with unlabeled lactose.
C) Measure the stoichiometry of ¹⁴C-labeled lactose covalently bound to protein to see if a 1:1 ratio is observed, and then use chemical analysis to identify the specific amino acids involved in the covalent bonds.
D) Determine how much radiolabel becomes covalently linked to the protein, and then repeat the experiment using protein with random amino acid substitutions throughout its polypeptide chain.
E) Identify amino acid residues that are covalently linked to ¹⁴C-lactose, and then repeat the experiment using a mutant version of the protein in which all of these residues are omitted from the polypeptide chain.