Figure 2.

Similarity of SSE1 to the 5′exonuclease domain of Thermus thermophilus (TTH) polymerase I. SSE1 was aligned to the first 277 aa of Tth polymerase I by using the clustal w program. Identities are shown in dark gray and similarities in light gray. The residues marked by ∗ are conserved among 18 bacterial and phage 5′ → 3′ exonucleases and have been shown to be involved with substrate binding or catalysis (20).