Table 2.
Cloned H. pylori addA and addB Genes Express ATP-dependent Exonuclease in E. coli Cells
| Plasmid | ATP-dependent ds DNA exonuclease (Units/mg extract protein) a | Efficiency of platingb |
|
|---|---|---|---|
| T4 | T4 2− | ||
| pBR322 | 18 ± 4 (4) | 1.0 | 1.0 |
| pMR3 (recBCD) | 140 ± 11 (6) | 0.94 | 8.3 × 10−7 |
| pETDuet-1 | 24 ± 5 (6) | 0.97 | 0.91 ± 0.04 |
| pSA405 (addA addB) | 880 ± 12(6) | 0.91 | 6.2 × 10−6 |
a
Extracts were prepared from transformants of E. coli strain V2831 (ΔrecBCD2731 <kan>) with pBR322 or pMR3 or transformants of E. coli strain V3060 (ΔrecBCD2731 <kan> DE3) with pETDuet-1 or its derivatives. Cells containing pETDuet-1 were harvested 3 hr after induction with 1 mM IPTG. Data are the mean ± SEM from the indicated number of extracts (n) from separate cultures.
b
Phage titer on E. coli strain V3060 (ΔrecBCD2731 <kan> DE3) with the indicated plasmid divided by the phage titer on strain V3060 with pBR322. Data are the mean from 3 separate experiments.