Question

You have two purified samples of protein Y: the wild-type (nonmutated) protein and a mutant version with a single amino acid substitution. When washed through the same gel-filtration column, mutant protein Y runs through the column more slowly than the normal protein. Which of the following changes in the mutant protein is most likely to explain this result?

(a) the loss of a binding site on the mutant-protein surface through which protein Y normally forms dimers
(b) a change that results in the mutant protein acquiring an overall positive instead of a negative charge
(c) a change that results in the mutant protein being larger than the wild-type protein
(d) a change that results in the mutant protein having a slightly different shape from the wild-type protein

Answer 1

The mutant protein Y likely has a slightly different shape from the wild-type protein, slowing its movement through the gel-filtration column, as shape is a key factor affecting protein migration in this context.

Step-by-step explanation:

When analyzing the behavior of a mutant protein Y running more slowly through a gel-filtration column compared to the wild-type protein, we can deduce that there might have been structural changes to the mutant protein. The most likely explanation for this observation is (d) a change that results in the mutant protein having a slightly different shape from the wild-type protein. A change in shape can affect how the protein interacts with the gel matrix, slowing its movement through the column. Options (a), (b), and (c) could theoretically cause a change in elution time, but (d) is more consistent with the fact that shape influences how a protein migrates in gel-filtration chromatography.