FIG. 3.
In vivo and in vitro effects of OAS on FhuR-dependent regulation in L. lactis. Upper panel: effect of OAS on expression of FhuR-regulated genes of L. lactis. Luciferase activities (104 lux/OD600) measured from JIM8499, JIM8543, and JIM8545 strains carrying the PmetB2-lux, PyjgC-lux, and PyhcE-lux fusions, respectively, grown in M17 medium with or without OAS. The x axis shows time of incubation relative to the addition of OAS (time zero). Symbols: ⋄, without OAS; ▪, with OAS at a final concentration of 1 mM; •, at 2 mM; ▴, at 3 mM; ♦, at 4 mM; ×, at 5 mM. Lower panel: OAS effect on FhuR-metB2 complex migration. The labeled DNA fragment containing the metB2 promoter region (10 × 10−15 mole) was incubated with different concentrations of purified FhuR protein (0 μM, 1.2 μM, and 3.6 μM) with an increasing concentration of OAS (0 mM, 20 mM, 40 mM, 60 mM, and 80 mM) and analyzed on nondenaturing polyacrylamide gel electrophoresis.