FIG. 7.

Comparison of human APE1 and exonuclease III from Escherichia coli. The structurally similar enzymes, human APE1 (PDB identifier, 1BIX, green ribbon rendering) and exonuclease III (PDB identifier, 1AKO, blue), share a similar fold; however, APE1 includes an additional 62 N-terminal residues, highlighted in red (residues 44-62). In exonuclease III, the residue equivalent to the APE1 Cys 65 (yellow stick rendering) is Val 4 (gray stick rendering). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article at www.liebertonline.com/ars).