FIG. 2.

Section of an autoradiograph after SDS-PAGE of [³⁵S]methionine-labeled N-His-FhuF protein. Strains H5385 pGP1-2 (lanes 1 and 2) and WM1576 (lanes 3 to 5) were transformed with plasmid pKF191, which allowed the exclusive expression of the gene encoding N-His-FhuF by the T7 RNA polymerase system (12, 16). Ten minutes after addition of [³⁵S]methionine, whole cells were pelleted by centrifugation and an aliquot was separated by SDS-PAGE (lanes 1 and 3). For the chase, the remaining cells were suspended in fresh medium containing 50 mM unlabeled methionine and incubated for 15 min (lane 4) and 30 min (lanes 2 and 5) before loading on the polyacrylamide gel.