Figure 7.

High‐affinity uptake of ⁵⁵Fe²⁺ in the presence of competing metal ions. High‐affinity ferrous iron transport using 0.1 μmol/L ⁵⁵Fe²⁺ was studied in Schu S4 and a fupA complemented ΔfslE ΔfupA mutant as described in the legend to Figure 1E. (A) High‐affinity transport of ferrous iron by Schu S4 is dependent on FupA. Uptake of 0.1 μmol/L ⁵⁵Fe²⁺ is only restored to a ΔfslE ΔfupA mutant when it is complemented by a wild‐type copy of fupA and not by vector (v) alone. (B) ⁵⁵Fe²⁺ uptake in the presence of competing metal ions. Reactions contained a 10‐fold molar excess of nonradioactive metal ions added as FeCl₃, CuCl₂, or ZnCl₂. Rates of uptake are represented as mean ± standard error of the mean (SEM) of assays done in triplicate. Experiments were repeated at least once more with similar results.