Table 2.
Kinetic analysis of wild type and mutant terminase enzymes. Steady state ATP hydrolysis was performed as described in Materials and Methods. 100% relative steady state activity corresponds to kobs = 2.7 ± 0.1 μM/min. Single turnover ATP hydrolysis was performed as described in Materials and Methods and the data presented in Figure 3C were fit to a single exponential time course to afford kobs; the best fit of each data set is indicated as a solid line in the Figure. 100% relative activity corresponds to kobs= (140 ± 4) x 10−3 s−1
| Enzyme | Steady state ATP hydrolysis (relative) | Single turnover ATP hydrolysis (relative) |
|---|---|---|
| Wild Type | 2.7 ± 0.1 μM/min (100%) | (140 ± 4) x 10−3 s−1 (100%) |
| E179A | 0.09 ± 0.01 μM/min (3.3%) | (1.9 ± 0.1) x 10−3 s−1 (1.4%) |
| E179Qa | 0.02 ± 0.06 μM/min (0.7%) | (0.25 ± 0.02) x 10−3 s−1 (0.2%) |
| E179D | 0.13 ± 0.2 μM/min (4.8%) | - |
aWe note that the ATPase activity observed with the most severely defective mutant enzyme (E179Q) represents an upper limit of activity and which could feasibly be associated with a contaminating cellular ATPase.