TABLE 5.

Specific activity of β-galactosidase in lrp⁺ and lrp strains having leuP-lacZ transcriptional fusions with upstream DNA at the λ attachment site^a

Strain	lrp allele	PilvIHb	leu attenuatorb	Sp. act. of β-galactosidasec		Ratio of sp. act. (without Leu/with Leu)
				Without Leu	With Leu
CV1543	lrp+	+	+	2,500 ± 250	96 ± 6.4	26
CV1544	lrp-35::Tn10	+	+	2,890 ± 189	36 ± 2.3	79
CV1547	lrp+	+	−	5,380 ± 473	3,370 ± 136	1.6
CV1548	lrp-35::Tn10	+	−	3,120 ± 338	2,510 ± 246	1.2
CV1549	lrp+	−	−	5,370 ± 454	3,340 ± 143	1.6
CV1550	lrp-35::Tn10	−	−	3,110 ± 267	2,430 ± 278	1.3

^aStrains were grown as described in Table 3. 

^b+, present; −, absent. 

^cSpecific activity is in Miller units. Values represent the means and standard deviations for multiple samples taken throughout log growth phase from at least two independent experiments. Similar results were obtained for cells grown to late log and early stationary phases of growth.