Figure 3.

Biochemical Characterization of the Mutant Terminase Enzymes. (A) cos-cleavage endonuclease activity was quantified as described in Methods. The TerL^λ-E179D enzyme possesses a strong, non-specific nuclease activity that precludes accurate quantitation of specific cleavage at the cos site (not shown). Each bar represents the normalized average activity of at least three independent experiments with standard deviations indicated with error bars. (B) Steady state ATPase activity quantified as described in Methods. Each bar represents the normalized average activity of at least three independent experiments with standard deviation indicated. (C) Single turnover ATP hydrolysis quantified as described in Methods: black •, wild type terminase; green ♦, E179A mutant terminase; red ◊, E179Q mutant terminase. Each data point represents the average of at least three independent experiments with standard deviations indicated (in some cases the error bars are obscured by the data point). The solid lines represent the best fit of the data which affords the rate constants presented in Table 2. (D) DNA packaging activity was quantified as described in Methods. Each bar represents the normalized average activity of at least three independent experiments with standard deviations indicated with error bars.