FIG. 2.

ATPase activity of HrtA is influenced by various physicochemical conditions. (A) Concentration of ATP required for saturation of enzymatic activity. HrtA (0.5 μM) was incubated with increasing concentrations of ATP at 20°C, and ATPase activity was measured. (B) ATPase activity determination at different temperatures. (C) Effect of temperature pretreatment on HrtA activity. HrtA was incubated at the indicated temperature for 20 min, and ATPase activity was determined at 20°C. (D) Influence of pH on HrtA ATPase activity. (E) Effect of divalent metal cations on HrtA activity. HrtA ATPase activity was determined with the indicated concentration of MnCl₂, MgCl₂, or CaCl₂. For all experiments, the average of triplicate ATPase activities is indicated; error bars represent one standard deviation from the mean.