Table 1.
Tolerance and stability of DNA inserted within β-lactamase
| Insert size | Sequence | Frame | β-Lactamase activity [(Carbr/Tetr) × 100]% | Reversion frequency (Carbr/Tetr) |
|---|---|---|---|---|
| Nonrepetitive | ||||
| 66 bp | Random | In-frame | 100 | 1 |
| 70 bp | Random | +1 frame | 0.0007 | 7 × 10−6 |
| 71 bp | Random | −1 frame | 0.001 | 1 × 10−5 |
| 513 bp | HIV RT | In-frame | 95.3 | NA |
| 1,044 bp | HIV RT | In-frame | 69.2 | NA |
| 1,614 bp | HIV RT | In-frame | 43.9 | NA |
| 1,618 bp | HIV RT | +1 frame | 0.0005* | 5 × 10−6 |
| Microsatellite | ||||
| 75 bp | (CA)13 | In-frame | 100 | 1 |
| 74 bp | (CA)11 | +2 frame | 0.0045 | 4.45 ×10−5 |
| 73 bp | (CA)12 | −2 frame | 0.0036 | 3.67 × 10−5 |
| 73 bp | (A)10 | +1 frame | 0.0032 | 3.23 × 10−5 |
| 73 bp | (G)10 | +1 frame | 0.0016 | 1.59 × 10−5 |
| Mismatch repair | ||||
| 75 bp (WT strain) | (CA)11 | +2 frame | 0.0075 | 7.5 × 10−5 |
| 75 bp (mutH strain) | (CA)11 | +2 frame | 2.55 | 2.55 × 10−2 |
*
β-Lactamase constructs containing inserts of 1 kb and 1.6 kb were derived from and tolerated as indicated in strain NM522. The tolerance for these large inserts was much lower in strain BL21: 1 kb, 7.5%; 1.6 kb, 0%. All other inserts were stable and tolerated as indicated in BL21. NA, not applicable.