FIG. 3.

NE-mediated loss of iron from Tf and Lf. (a) Urea-PAGE of iron-saturated Tf after incubation for 18 h at 37°C in the absence of NE (lane 0) or in the presence of 5, 50, or 250 μM NE or 10 mM DHBA (lanes 5, 50, 250, and D, respectively). Lanes D, F, and S show the effect of incubation with DHBA (10 mM), 250 μM NE plus excess iron [1 mM Fe(NO₃)₃], and 250 μM NE-S, respectively. Lane M contains marker isoforms of Tf, fully saturated (diferric, Fe₂Tf), monoferric isoforms with iron occupying the N-terminal or C-terminal domain (Fe-Tf and Tf-Fe, respectively), and iron-free Tf (apo-Tf). (b) Viable counts of E. coli strain E2348/69 after 18 h of incubation from an inoculum of 10² CFU/ml in serum-SAPI medium supplemented with NE or NE-S at the concentrations indicated for panel a above. (c) SDS-PAGE of iron-saturated Lf after incubation for 18 h at 37°C in the absence of NE (lane 0) or in the presence of 5, 50, or 250 μM NE (lanes 5, 50, and 250, respectively). Fe-Lf and apo-Lf indicate the mobility of iron-bound and iron-free isoforms of Lf, respectively.