Molecular Biology of the Gene 7th Edition by Richard Losick, James Watson, Michael Levine, Tamara Baker, Alexander Gann

Exercise 14

Researchers characterized a human protein with a role in Holliday junction resolution. They purified and used the protein in an assay with the DNA substrate shown below on the left. Each of the four strands of DNA (A, B, C, D) is 60 nucleotides (nt) long, and only the DNA strand marked A is end-labeled with 5?- 32 P. The researchers set up three reactions with the DNA substrate, incubating (1) with no protein, (2) with the purified protein (Protein X), and (3) with RecA (as a control). The products from each reaction were run in separate lanes of a denaturing polyacrylamide gel. An autoradiogram of the gel is shown below on the right.

A. Given these data, propose a function for Protein X.
B. Based on your answer in part A, this protein functions similarly to what E. coli protein?