FIG. 2.

Time course experiment showing (by 6 M urea–polyacrylamide gel electrophoresis) the removal of iron from diferric human transferrin by S. aureus. Staphylococci (10⁸ CFU/ml) were incubated in PBS buffer plus glucose with 250 μg of diferric human transferrin at 37°C for 0 (lane 1), 5 (lane 2), 10 (lane 3), 20 (lane 4), 30 (lane 5), and 60 (lane 6) min. Cells were pelleted by centrifugation, and the supernatant was loaded onto a 6 M urea–polyacrylamide gel. Human apotransferrin (lane 7) and a mixture of human diferric and monoferric N-lobe transferrin (lane 8) are shown as controls. The positions of diferric (DF), monoferric N-lobe (MN), and monoferric C-lobe (MC) transferrins and apotransferrins (AP) are indicated on the right- and left-hand sides of the figure.