Table 3.
Pi release parameters during ssDNA translocation
| Protein | Polythymidylate length, bases | Rapid-phase amplitude, P/PcrA | Rapid-phase duration, s | Rapid-phase rate, s−1 | Steady-state rate, s−1 |
|---|---|---|---|---|---|
| Wild type | 7 | 2.1 | 0.09 | 22.2 | 4.7 |
| 12 | 4.5 | 0.14 | 33.2 | 4.8 | |
| 17 | 7.0 | 0.16 | 46.5 | 5.8 | |
| F192A | 7 | 0.48* | NA | NA | 8.8 |
| 12 | 0.85* | NA | NA | 14.5 | |
| 17 | 0.80* | NA | NA | 15.2 | |
| H587A | 7 | 4.1 | 0.20 | 20.8 | 4.5 |
| 12 | 7.0 | 0.25 | 28.4 | 5.0 | |
| 17 | 6.9 | 0.32 | 21.3 | 4.6 | |
| F626A | 7 | 2.0 | 0.09 | 21.7 | 1.8 |
| 12 | 3.1 | 0.18 | 17.2 | 2.6 | |
| 17 | 4.0 | 0.23 | 17.3 | 3.1 |
Rapid-phase amplitude and duration are shown for wild type, F192A, H587A, and F626A PcrA⋅ssDNA complexes with polythymidylates of 7, 12, and 17 bases in length. NA, not available.
*
The rapid phase of Pi release for the F192A mutant represents a true “phosphate burst” rather than a multiple turnover linear phase as in the wild-type protein.