D2(teal blue), E1 (dark blue), and E2(red) metastable states showing the gating of O1-helix and preinsertion base insertion into the preinsertion site (circled area). The additional part of pol-I-DNA complex is shown to demonstrate a fair alignment of the rest of the protein. Notice the fluctuation of the loop connecting O-helix with O1-helix. The positions of Cα atoms of G715 (in the loop area) and G711 (at the base of the O-helix) are also shown as spheres. (θ, δ, β)D2 = (61, 1.9, 13); (θ, δ, β)E1 = (65, 5.9, 10); (θ, δ, β)E2 = (65, 5.6, 7.1). Preinsertion base is shown as sticks; the rest of DNA is shown as lines for E1, as well as tubes for D2, E1, and E2. Y714 is shown as lines.