FIG. 5.
Effect of PII on the rate of ATP cleavage in the coupled assay system. Reactions were performed and the results were analyzed as described in Materials and Methods. For both panels, the data point plotted on the y axis is the rate obtained in the absence of PII. (A) Effect of PII when NRI-N was limiting. Reaction mixtures contained 1 μM NRII, 0.75 μM NRI-N, 50 μM 2-ketoglutarate, the indicated concentrations of PII, and other components as detailed in Materials and Methods. (B) Effect of PII when NRII was limiting. Reaction mixtures contained 0.4 μM NRII, 12 μM NRI-N, 50 μM 2-ketoglutarate, the indicated concentrations of PII, and other components as detailed in Materials and Methods. The apparent Ki for this experiment is ∼0.6 μM PII. Vo, rate of ATP cleavage.