title: Structural investigations into the interaction of hemoglobin and part structures with bacterial endotoxins.
abstract: An understanding of details of the interaction mechanisms of bacterial endotoxins (lipopolysaccharide, LPS) with the oxygen transport protein hemoglobin is still lacking, despite its high biological relevance. Here, a biophysical investigation into the endotoxin:hemoglobin interaction is presented which comprises the use of various rough mutant LPS as well as free lipid A; in addition to the complete hemoglobin molecule from fetal sheep extract, also the partial structure alpha-chain and the heme-free sample are studied. The investigations comprise the determination of the gel-to-liquid crystalline phase behaviour of the acyl chains of LPS, the ultrastructure (type of aggregate structure and morphology) of the endotoxins, and the incorporation of the hemoglobins into artificial immune cell membranes and into LPS. Our data suggest a model for the interaction between Hb and LPS in which hemoglobins do not react strongly with the hydrophilic or with the hydrophobic moiety of LPS, but with the complete endotoxin aggregate. Hb is able to incorporate into LPS with the longitudinal direction parallel to the lipid A double-layer. Although this does not lead to a strong disturbance of the LPS acyl chain packing, the change of the curvature leads to a slightly conical molecular shape with a change of the three-dimensional arrangement from unilamellar into cubic LPS aggregates. Our previous results show that cubic LPS structures exhibit strong endotoxic activity. The property of Hb on the physical state of LPS described here may explain the observation of an increase in LPS-mediating endotoxicity due to the action of Hb.
authors.affiliation: Forschungszentrum Borstel, Leibniz-Zentrum für Medizin und Biowissenschaften, Borstel, Germany.
authors.forename: Jörg
authors.initials: J
authors.lastname: Howe
authors.forename: Patrick
authors.initials: P
authors.lastname: Garidel
authors.forename: Manfred
authors.initials: M
authors.lastname: Roessle
authors.forename: Walter
authors.initials: W
authors.lastname: Richter
authors.forename: Christian
authors.initials: C
authors.lastname: Alexander
authors.forename: Karin
authors.initials: K
authors.lastname: Fournier
authors.forename: Jean Pierre
authors.initials: JP
authors.lastname: Mach
authors.forename: Thierry
authors.initials: T
authors.lastname: Waelli
authors.forename: Reginald M
authors.initials: RM
authors.lastname: Gorczynski
authors.forename: Artur J
authors.initials: AJ
authors.lastname: Ulmer
authors.forename: Ulrich
authors.initials: U
authors.lastname: Zähringer
authors.forename: Alfred
authors.initials: A
authors.lastname: Hartmann
authors.forename: Ernst Th
authors.initials: ET
authors.lastname: Rietschel
authors.forename: Klaus
authors.initials: K
authors.lastname: Brandenburg
mesh_terms: D000818:Animals; D002417:Cattle; D005260:Female; D006454:Hemoglobins / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D008070:Lipopolysaccharides / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D008854:Microscopy, Electron; D008956:Models, Chemical; D011247:Pregnancy; D011485:Protein Binding; D019779:Salmonella enterica; D053838:Scattering, Small Angle; D012756:Sheep; D017550:Spectroscopy, Fourier Transform Infrared; D014961:X-Ray Diffraction
chemical_list: D006454:Hemoglobins; D008070:Lipopolysaccharides