CHARACTERIZATION OF A HEMOGLOBIN PROTEASE SECRETED BY THE PATHOGENIC ESCHERICHIA-COLI STRAIN EB1

Many pathogenic bacteria can use heme compounds as a source of iron. P athogenic Escherichia coli strains are capable of using hemoglobin as an iron source. However, the mechanism of heme acquisition from hemogl obin is not understood for this microorganism. We present the first mo lecular characterization of a hemoglobin protease (Hbp) from a human p athogenic E. coli strain. The enzyme also appeared to be a heme-bindin g protein. Affinity purification of this bifunctional protein enabled us to identify the extracellular gene product, and to clone and analyz e its gene. A purification procedure developed for Hbp allowed us to p erform functional studies. The protein interacted with hemoglobin, deg raded it and subsequently bound the released heme. These results sugge st that the protein is involved in heme acquisition by this human path ogen. Hbp belongs to the so-called IgA1 protease-like proteins, as ind icated by the kinetics of its membrane transfer and DNA sequence simil arity. The gene of this protein appears to be located on the large pCo lV-K30 episome, that only has been isolated from human and animal path ogens. All these characteristics indicate that Hbp may be an important virulence factor that may play a significant role in the pathogenesis of E. coli infections.