FIGURE 8.

Toward a mechanism based on conformational selection. A, minimal plausible kinetic scheme includes three states. For the apo-form, E, and each of the complexes: E:p/t, E:dNTP, E:p/t:dNTP_(correct), and E:p/t:dNTP_(incorrect), the interchange of KT^DA between its various conformational states is illustrated. Each conformational state is depicted by a colored circle: blue, red and green for O, C, and NB, respectively. The relative area of each circle qualitatively represents the relative populations of each state at equilibrium. The arrow lengths qualitatively represent to the relative forward and reverse rates and are proportional to its reaction rate. B, presence of an additional transient intermediate which acts as a hub between states cannot be excluded by our analysis.