title: Isolation of an outer membrane hemin-binding protein of Haemophilus influenzae type b.
abstract: Haemophilus influenzae is a heme-dependent bacterium. However, little is known of the heme-iron uptake mechanism in this organism. By using a batch ligand affinity chromatography method, a hemin-binding protein of 39,500 molecular weight was isolated from total membranes derived from H. influenzae type b grown under iron-depleted but not under iron-sufficient conditions. Detection of the hemin-binding protein in a whole-cell binding assay demonstrated a surface-exposed location. Competition binding experiments indicated that this hemin-protein interaction was specific, since only hemin or heme-containing proteins, such as human hemoglobin and bovine catalase, but not protoporphyrin IX, iron-loaded human lactoferrin, or transferrin, could abrogate binding. In a limited survey of other H. influenzae strains, an identical hemin-binding protein was isolated, implying that this polypeptide may be structurally and functionally conserved among strains.
authors.affiliation: Department of Microbiology and Infectious Diseases, University of Calgary, Alberta, Canada.
authors.forename: B C
authors.initials: BC
authors.lastname: Lee
mesh_terms: D001425:Bacterial Outer Membrane Proteins / Q000032:analysis / Q000302:isolation & purification*; D002352:Carrier Proteins / Q000032:analysis / Q000302:isolation & purification*; D006193:Haemophilus influenzae / Q000737:chemistry*; D000081062:Heme-Binding Proteins; D006420:Hemeproteins / Q000032:analysis / Q000302:isolation & purification*; D033862:Iron-Binding Proteins; D033863:Transferrin-Binding Proteins; D001618:beta-Lactamases / Q000032:analysis
chemical_list: D001425:Bacterial Outer Membrane Proteins; D002352:Carrier Proteins; D000081062:Heme-Binding Proteins; D006420:Hemeproteins; D033862:Iron-Binding Proteins; D033863:Transferrin-Binding Proteins; D001618:beta-Lactamases