Table 3. Effect of Mlc and NagC operator sequences on expression of ptsG–lacZ and nagBE–lacZ fusions.
| Plasmid |
Strain |
Derepression |
|
| |
|
ptsG–lacZ |
nagBE–lacZ |
| M26 |
w.t |
13.1 |
1.3 |
| M1 |
w.t. |
11.5 |
1.8 |
| M11 |
w.t. |
6.5 |
2.6 |
| M3 |
w.t. |
5.8 |
1.8 |
| M134 |
w.t. |
2.2 |
5.4 |
| C24 |
w.t. |
1 |
4.7 |
| C17 |
w.t. |
1 |
5.3 |
| C5 |
w.t. |
1 |
5.5 |
| C43 |
w.t. |
1 |
7.5 |
| C42 |
w.t. |
1 |
8.1 |
| C9 |
w.t. |
1 |
8.2 |
| pTZ(Nag14E-15B) |
w.t. |
1.1 |
15 |
| pTZ19 |
w.t. |
1 |
1 |
| pTZ19 | mlc nagC | 13 | 35 |
JM101(mlc+, nagC+), lysogenised with either λRS/nagBE–lacZ or λRS/ptsG–lacZ, was transformed with pTZ19R carrying the NagC and Mlc selected binding sites indicated. Bacteria were grown in MOPS medium containing 0.4% glycerol, 0.5% cas amino acids 0.5 mg ampicillin/ml at 30°C and β-galactosidase activities were measured at the end of the exponential phase (A650 = 0.6–0.8). Derepression caused by the operators in trans was calculated by comparison with the presence of pTZ19R. Maximum derepression of the fusions was measured in JM101 carrying nagC::Cm and mlc::Tc mutations. The basal levels of expression are 6 and 60 U for ptsG–lacZ and nagBE–lacZ, respectively. Results are the mean of two independent cultures.