. 2009 Oct 23;192(1):225–232. doi: 10.1128/JB.00829-08

TABLE 1.

RhaS repression of various rhaSR promoter fusions

Φ(rhaS-lacZ) promoter truncation	Avg β-galactosidase activity (Miller units)^a in a strain carrying:		Fold repression by RhaS
Φ(rhaS-lacZ) promoter truncation	Vector only^b	rhaS⁺ plasmid^b	Fold repression by RhaS
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.

The vector was pSE262 (34), which is pHG165 (26) with a stronger promoter driving expression. RhaS was expressed from plasmid pSE265 (34), which is pSE262 rhaS⁺.