title: Haemophilus influenzae stores and distributes hemin by using protein E.
abstract: The human pathogen Haemophilus influenzae causes mainly respiratory tract infections such as acute otitis media in children and exacerbations in patients with chronic obstructive pulmonary disease. We recently revealed the crystal structure of H. influenzeae protein E (PE), a multifunctional adhesin that is involved in direct interactions with lung epithelial cells and host proteins. Based upon the PE structure we here suggest a hypothetical binding pocket that is compatible in size with a hemin molecule. An H. influenzae mutant devoid of PE bound significantly less hemin in comparison to the PE-expressing wild type counterpart. In addition, E. coli expressing PE at the surface resulted in a hemin-binding phenotype. An interaction between hemin and recombinant soluble PE was also demonstrated by native-PAGE and UV-visible spectrophotometry. Surface plasmon resonance revealed an affinity (Kd) of 1.6 × 10(-6)M for the hemin-PE interaction. Importantly, hemin that was bound to PE at the H. influenzae surface, was donated to co-cultured luciferase-expressing H. influenzae that were starved of hemin. When hemin is bound to PE it thus may serve as a storage pool for H. influenzae. To our knowledge this is the first report showing that H. influenzae can share hemin via a surface-located outer membrane protein.
authors.affiliation: Medical Microbiology, Department of Laboratory Medicine Malmö, Lund University, SE-205 02 Malmö, Sweden.
authors.forename: Tamim
authors.initials: T
authors.lastname: Al Jubair
authors.affiliation: Medical Microbiology, Department of Laboratory Medicine Malmö, Lund University, SE-205 02 Malmö, Sweden.
authors.forename: Birendra
authors.initials: B
authors.lastname: Singh
authors.affiliation: Medical Microbiology, Department of Laboratory Medicine Malmö, Lund University, SE-205 02 Malmö, Sweden.
authors.forename: Christophe
authors.initials: C
authors.lastname: Fleury
authors.affiliation: Protein Chemistry, Department of Laboratory Medicine Malmö, Lund University, SE-205 02 Malmö, Sweden.
authors.forename: Anna M
authors.initials: AM
authors.lastname: Blom
authors.affiliation: Section of Clinical and Experimental Infectious Medicine, Department of Clinical Sciences, Lund University, SE-221 84 Lund, Sweden.
authors.forename: Matthias
authors.initials: M
authors.lastname: Mörgelin
authors.affiliation: Department of Biochemistry and Structural Biology, Lund University, SE-221 00 Lund, Sweden.
authors.forename: Marjolein M
authors.initials: MM
authors.lastname: Thunnissen
authors.affiliation: Medical Microbiology, Department of Laboratory Medicine Malmö, Lund University, SE-205 02 Malmö, Sweden. Electronic address: kristian.riesbeck@med.lu.se.
authors.forename: Kristian
authors.initials: K
authors.lastname: Riesbeck
mesh_terms: D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001665:Binding Sites; D017353:Gene Deletion; D006193:Haemophilus influenzae / Q000235:genetics / Q000378:metabolism*; D006427:Hemin / Q000378:metabolism*; D008958:Models, Molecular; D011485:Protein Binding; D011487:Protein Conformation; D020349:Surface Plasmon Resonance
chemical_list: D001425:Bacterial Outer Membrane Proteins; D006427:Hemin
keywords: Haemophilus influenzae; Hemin; Protein E