Scheme 4.

Kinetic Schemes for Sequenase–dP/T⁺ (SqD⁺) Trapping of dTTP(N) Released from the RB69 pol–dP/T*–dTTP Ternary Complex (FD*N)^a

^a We assume that ED* + N and (ED*N)^O are in rapid equilibrium as (ED*N)^O is a collision complex. (FD*N)^C1 and (FD*N)^C2 are in a different fluorescent state than (ED*N)^O. Scheme A1 or A2, combined with scheme B, is consistent with the experimental data. The superscripts C1, C2, and O denote two putative closed forms of the ternary complex and the open, collision complex, respectively. D* indicates a dP/T with dAP as the templating base, and D⁺ indicates a dP/T labeled at the 5′ end of the template with Cy3.