Figure 4

Regulation of selected target genes by heterologous Lrp proteins. E. coli strains, all carrying lrp-Tn10 and Δlac, were transformed with plasmids carrying various lrp alleles (or vector control). Transformants were grown in unsupplemented MOPS glucose medium. A. Western blot analysis of Lrp accumulation (Eco, E. coli Lrp; Pmi, P. mirabilis Lrp; Vch, V. cholerae Lrp; pCC1, vector control) using polyclonal antiserum raised against E. coli Lrp. The arrow indicates the direction of electrophoresis. B-D. Plrp-lacZ (B), PgltB-lacZ (C) and PlivK-lacZ (D) activity were measured via ONPG hydrolysis, and plotted vs. culture density to ensure that the cultures were in balanced growth. The Lrp orthologs used are from P. mirabilis (triangles) and V. cholerae (squares), as well as the E. coli positive control (circles) and the vector control (diamonds). E-G. Isoleucine, Leucine and Valine was added to the medium ("+Leu") for experiments depicted in the lower panels: Plrp-lacZ (E), PgltB-lacZ (F) and PlivK-lacZ (G). The correlation coefficients for the least-squares fits to the data were all at least 0.97.