Fig. 1.

Rev1 binary and ternary crystal structures. (A) The time-lapse X-ray crystallography approach. The ligands bound to each Rev1 state are indicated at the bottom. An active site close-up of the Rev1 (B) binary and (C) ternary crystal structures. The nucleic acid residues are shown in yellow and Rev1 in gray. A Fo–Fc OMIT map contoured at σ = 3.0 around the two active-site calcium ions, incoming dCTP, and primer terminal dG is shown as a green mesh. (D and E) An overlay of the Rev1 binary (gray sticks) and ternary (yellow sticks) complexes are shown in two orientations to indicate the movement at the primer termini, phosphate backbone, and R518. Key protein and DNA residues are indicated in each panel.