TABLE 1.
Φ(rhaS-lacZ) promoter truncation | Avg β-galactosidase activity (Miller units)a in a strain carrying: |
Fold repression by RhaS | |
---|---|---|---|
Vector onlyb | rhaS+ plasmidb | ||
Δ85 | 8.9 | 7.0 | 1.3 |
Δ103 | 10 | 2.7 | 3.7 |
Δ114 | 12 | 2.9 | 4.1 |
Δ122 | 155 | 5.3 | 29 |
Δ128 | 204 | 6.9 | 30 |
Δ216 | 234 | 7.1 | 33 |
Δ312 | 203 | 4.9 | 41 |
Δ312 CRP− | 22 | 3.5 | 6.3 |
β-Galactosidase activity was assayed from single-copy rhaS-lacZ fusions with the upstream promoter endpoints indicated. The Δ312 CRP− promoter has point mutations in three consensus positions of the rhaSR promoter CRP binding site. Cultures were grown in MOPS-buffered minimal growth medium containing ampicillin and l-rhamnose. The strain background was ΔrhaS rhaR+ zih-35::Tn10 recA::cat. The standard errors were less than 12% of the average activities.