title: Identification and characterization of a heme periplasmic-binding protein in Haemophilus ducreyi.
abstract: Haemophilus ducreyi, a gram-negative and heme-dependent bacterium, is the causative agent of chancroid, a genital ulcer sexually transmitted infection. Heme acquisition in H. ducreyi proceeds via a receptor mediated process in which the initial event involves binding of hemoglobin and heme to their cognate outer membrane proteins, HgbA and TdhA, respectively. Following this specific interaction, the fate of the periplasmic deposited heme is unclear. Using protein expression profiling of the H. ducreyi periplasmic proteome, a periplasmic-binding protein, termed hHbp, was identified whose expression was enhanced under heme-limited conditions. The gene encoding this protein was situated in a locus displaying genetic characteristics of an ABC transporter. The purified protein bound heme in a dose-dependent and saturable manner and this binding was specifically competitively inhibited by heme. The hhbp gene functionally complemented an Escherichia coli heme uptake mutant. Expression of the heme periplasmic-binding protein was detected in a limited survey of H. ducreyi and H. influenzae clinical strains. These results indicate that the passage of heme into the cytoplasm of H. ducreyi involves a heme dedicated ABC transporter.
authors.affiliation: Department of Biochemistry, Microbiology, and Immunology, Faculty of Medicine, University of Ottawa, Ottawa, ON K1H 8M5, Canada.
authors.forename: Melissa
authors.initials: M
authors.lastname: St Denis
authors.forename: Brigitte
authors.initials: B
authors.lastname: Sonier
authors.forename: Renée
authors.initials: R
authors.lastname: Robinson
authors.forename: Fraser W
authors.initials: FW
authors.lastname: Scott
authors.forename: D William
authors.initials: DW
authors.lastname: Cameron
authors.forename: B Craig
authors.initials: BC
authors.lastname: Lee
mesh_terms: D015153:Blotting, Western; D015180:Electrophoresis, Gel, Two-Dimensional; D004591:Electrophoresis, Polyacrylamide Gel; D020869:Gene Expression Profiling; D006191:Haemophilus ducreyi / Q000235:genetics; D006418:Heme / Q000378:metabolism*; D049449:Luminescence; D033902:Periplasmic Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D020543:Proteome / Q000235:genetics
chemical_list: D033902:Periplasmic Binding Proteins; D020543:Proteome; D006418:Heme