FIG. 3.
Binding and transport of FeEnt by FepA homologs. The concentration dependence of FeEnt binding (A) and transport (C) was measured for chromosomally expressed FepA of E. coli (•) and S. typhimurium (▴) grown in MOPS medium, and P. aeruginosa (■) and B. bronchisepticus (▾) cultured in MOPS medium with enterobactin (2 μM). Binding (B) and transport (D) of FeEnt was also measured for the individual proteins EcoFepA (○), StyFepA (▵), StyIroN (◊), PaeFepA (□), and BpeFepA (▿), expressed from plasmids in E. coli. Insets show transport of FeEnt by E. coli FepA at concentrations near the Km. The plotted data represent mean values (with standard deviations) normalized to Vmax from seven experiments. These curves gave Hill coefficients of 2.98 and 3.19 for chromosome- and plasmid-expressed FepA, respectively, with standard errors less than 5%.