FIG. 7.

Localization of cell-associated iron, NE, and Tf in growing bacteria. (a and b) Distribution of Tf-derived ⁵⁵Fe and [³H]NE, respectively, in membrane (M), soluble (S), and wash (W) fractions following ultracentrifugation of sonicated bacteria. (c) Western blot analysis of membrane (M) and soluble (cytoplasmic/periplasmic, S) proteins (approximately 25 μg of protein separated by SDS-PAGE) probed with anti-Tf antibodies. Lane Tf contains 1 μg of purified human Tf; the arrow indicates the position of the mature protein.