TABLE 1.
Effects of HAMP and S-helix alterations on NarX negative function: NarL(V88A)-dependent Φ(narG-lacZ) expressiona
| Alterationb | LacZ sp act |
Induction ratioc | |
|---|---|---|---|
| − Nitrate | + Nitrate | ||
| None (vector only) | 1,270 | 1,150 | 0.9 |
| None (wild type) | 200 | 1,440 | 7.2 |
| Δ(S220-L223) | 330 | 140 | 0.4 |
| Δ(L223-S226) | 170 | 74 | 0.4 |
| Δ(Y227-L258) | 2,050 | 1,150 | 0.6 |
| Δ(V234-G240) | 7 | 150 | 21 |
| Δ(K237-H243) | 7 | 890 | 127 |
| Δ(K244-F250) | 56 | 1,390 | 25 |
| Δ(L251-R257) | 2,660 | 1,390 | 0.5 |
| R233E | 18 | 1,350 | 75 |
| L241A | 280 | 1,370 | 4.9 |
a
Strains were cultured anaerobically to the mid-exponential phase in enriched medium (TY broth plus a 1:1 mixture of MOPS-glucose). Nitrate was added as indicated at 40 mM.
b
Alteration on the indicated narX allele on plasmid pVJS2474 derivative in strain VJS4033 [Φ(narG-lacZ) ΔnarX242 narQ251::Tn10 narL505 pcnB+].
c
The induction ratio is calculated as the LacZ specific activity from the nitrate-supplemented culture divided by activity from the unsupplemented culture (minus nitrate).