Figure 1.
Stereo diagram of the interactions between the side chain of Arg-660 and the incoming base. In the protein, only the O helix is represented and is colored in red, gold, dark blue, and dark green for the ddCTP-, ddATP-, ddTTP-, and ddGTP-trapped complexes, respectively. In the DNA, only the dCMP/ddGTP pair is represented and is colored in green. H-bond interactions between Arg-660 and the O6 and N7 atoms in the base of the ddGTP are indicated by lines. Distances between atoms involved in H-bonds are indicated.