FIG. 7.

Diagram of the equilibria affecting the concentration of the excision complex (RT with the T/P bound in the N site and an appropriately bound pyrophosphate donor). Factors that can affect the equilibria, such as dNTPs favoring the formation of the ternary complex or the azido group of AZT favoring the formation of the binary complex, are shown near the appropriate arrow. Some factors, such as the presence of M184V or the base composition near the 3′ end of the primer, are known to affect the overall efficiency of excision (4), but it is not clear which of the equilibria are affected. These are listed below the diagram.