Figure 8.

HapX is an iron-binding protein. (A) E. coli cells were transformed with pET28 encoding HapX^WT and cultured in a medium containing 1 mM IPTG (red), with or without 1 mM BPS, for 2 hr at 37°. Cells were centrifuged and cell pellets were photographed. (B) HapX purified from cells grown in a medium containing 1 mM IPTG (red), or in a medium containing 1 mM IPTG and 1 mM BPS (blue) was analyzed using the UV-visible spectrophotometer. HapX purified from cells grown in the presence of 1 mM IPTG and 1 mM BPS was treated with sodium dithionite (SDT; green), and also analyzed. (C) Iron content of HapX purified from cells grown in a medium containing 1 mM IPTG (HapX), or 1 mM IPTG and BPS (HapX+BPS). The iron content of HapX purified from cells grown in the presence of 1 mM IPTG and treated with SDT (HapX+SDT) was also determined. Three biological replicates were analyzed. **P < 0.01.