Isolation of a hemin and hemoglobin binding outer membrane protein of Vibrio vulnificus biotype 2 (serogroup E)

The eel pathogen Vibrio vulnificus biotype 2 (serogroup E) is able to use hemin (Hm) or hemoglobin (Hb) as the sole iron source for growth in vitro and in vivo. The mechanism of heme-iron acquisition in this bacterium requires a direct interaction through binding sites on the bacterial surface (constitutive outer membrane proteins). Using affinity chromatography techniques, a unique protein of around 36.5 kDa was isolated from cell envelopes of E86 strain regardless of the affinity ligand used, hemoglobin or hemin. This protein was purified from both iron-enriched and iron-restricted grown cells. These results support the hypothesis that in this pathogen Hm- and Hb-iron acquisition is mediated by a common protein receptor which recognizes the heme prosthetic group of Hb.