Fig. 1.

Gallus FAN1 is an endonuclease. FAN1 cleaves preferentially 5′ flaps. The wild-type (WT) enzyme or the D977A (DA) mutant was incubated with a series of oligonucleotide substrates shown below the panel. The arrow indicates the preferred cleavage product. The rapidly migrating radioactive species seen at the bottom of this 20% denaturing polyacrylamide gel correspond to DNA fragments 1–4 nucleotides in length. The position of the radiolabel is indicated by an asterisk. M, marker; 3-WJ: three-way junction.