Figure 5.

Effects of translocating the tryptophan residue protruding from the surface of the APE1 active site. (A) Detection of AP endonucleolytic activity of APE1 mutants. DNA substrate (AP-dsDNA: 4.4 pmol), in which the oligonucleotide containing an AP site was 5′ ³²P-labeled, was incubated with the wild-type APE1 or its mutant (0.04 pmol). The DNA products were analyzed using a 20% denaturing polyacrylamide gel. (B) Ability of APE1 mutants to form a complex with the dsDNA containing an AP site. AP-dsDNA (0.45 pmol) was incubated with the wild-type APE1 or its mutant (4.5 pmol). The protein–DNA complexes were analyzed using a 15% native polyacrylamide gel.