FIG 3.
The HbpA proteins from the Austrian strains bind Hb and Hb-Hp. (A) The indicated strains were grown in low-iron PGTH (2 μM EDDA) medium, and supernatant (S) and cellular (C) protein fractions are shown. Proteins were separated by SDS-PAGE and then stained with Coomassie blue (bottom panel) or assessed for binding to Hb or Hb-Hp as indicated using an in situ method. Arrows indicate HbpA protein bands in the Coomassie blue-stained panel. (B) Purified recombinant HbpA protein (0.25 μg per lane) derived from strain 1737, 07-18, or 09-15 was assessed as for panel A. Representative experiments are shown for panels A and B. (C) Binding of HbpA to Hb and Hb-Hp was measured by ELISA as described in Materials and Methods. EC50 values were calculated using GraphPad Prism v9.1.2. Results show the mean and standard deviation from three experiments.