TABLE 4.
Effect of introducing mutations in the modE operator site on napF-lacZ expression in response to anaerobiosis and nitrate addition
| Strain | Relevant genotype | Mutations in ModE binding sitea | β-Galactosidase activityb
|
In vitro ModE bindingc | ||
|---|---|---|---|---|---|---|
| + O2, −NO3− | − O2
|
|||||
| −NO3− | +NO3− | |||||
| MC4100 | λHW2 | CGCTATATA-N6-TTTATAACC | 50 | 280 | 1,250 | Wild type |
| PM8 | λHW2 modE | 25 | 85 | 130 | ||
| MC4100 | λPM54 | CGCaAaATA-N6-TTTATAACC | 30 | 90 | 140 | Absent |
| PM8 | λPM54 modE | 25 | 90 | 135 | ||
| MC4100 | λPM55 | CGCTATAat-N6-TTTATAACC | 30 | 100 | 150 | Seven-fold reduction |
| PM8 | λPM55 modE | 30 | 85 | 125 | ||
a
Prophage λHW2 carries a copy of the wild-type ModE binding site. The mutations in the ModE binding site carried on the prophages λPM54 and -55 are underlined and shown in lowercase. All prophages are inserted in the chromosome of strains MC4100 and PM8 in single copy.
b
Units are given in nanomoles of ONPG hydrolyzed per minute per milligram of protein. Cells were grown in minimal glucose medium under aerobic and anaerobic conditions as described in the text. Sodium nitrate (NO3−) was added (at 40 mM) where indicated.
c
In vitro binding was measured via gel shift assays.