Structural comparison of Pfu Hjm with the A. fulgidus Hel308-DNA complex. (A) Hjm (colored as in Figure 1) was fitted to Hel308 (protein and DNA are colored grey and blue, respectively), by superimposing each domain individually. First, Domain 2 of Hjm was fitted, and then the other domains were separately moved to the best-fit positions. Shift values on the second fitting are indicated. (B) Sulfate ion binding sites in the Hjm Form 1 crystals. The protein is represented as a surface colored by electrostatic potential, calculated by the program GRASP . The DNA structure is that in the Hel308-DNA complex. The boxed region is shown by a transparent surface to show the sulfate ions located inside of the protein.