TABLE 2.

Specific activity of β-galactosidase in lrp⁺ and lrp strains having a leuPAB′-lacZ translational fusion^a

Strain	lrp allele	Sp. act. of β-galactosidaseb
CP55	lrp+	334 ± 46
CV1512	lrp-35::Tn10	19.5 ± 2.4
CV1513	lrp+	166 ± 11
CV1514	lrp-35::Tn10	16.2 ± 0.6

^aStrains were grown at 37°C with shaking in SSA minimal salts (11) containing 0.2% glucose; 50 μg (each) of isoleucine, valine, leucine, and proline per ml; and 5 μg of thiamine per ml. Cultures were grown overnight and diluted to an A₅₅₀ of 0.01, and samples were taken at different times in the log phase for assay. 

^bSpecific activity is in Miller units (15). β-Galactosidase assays were performed as described previously (12, 13). Values represent the means and standard deviations for multiple samples taken throughout the log growth phase from at least two independent experiments.