title: Crystal Structure of a Complex of Surfactant Protein D (SP-D) and Haemophilus influenzae Lipopolysaccharide Reveals Shielding of Core Structures in SP-D-Resistant Strains.
abstract: The carbohydrate recognition domains (CRDs) of lung collectin surfactant protein D (SP-D) recognize sugar patterns on the surface of lung pathogens and promote phagocytosis. Using Haemophilus influenzae Eagan strains expressing well-characterized lipopolysaccharide (LPS) surface structures of various levels of complexity, we show that bacterial recognition and binding by SP-D is inversely related to LPS chain extent and complexity. The crystal structure of a biologically active recombinant trimeric SP-D CRD complexed with a delipidated Eagan 4A LPS suggests that efficient LPS recognition by SP-D requires multiple binding interactions utilizing the three major ligand-binding determinants in the SP-D binding pocket, with Ca-dependent binding of inner-core heptose accompanied by interaction of anhydro-Kdo (4,7-anhydro-3-deoxy-d-manno-oct-2-ulosonic acid) with Arg343 and Asp325. Combined with enzyme-linked immunosorbent assays (ELISAs) and fluorescence-activated cell sorter (FACS) binding analyses, our results show that extended LPS structures previously thought to be targets for collectins are important in shielding the more vulnerable sites in the LPS core, revealing a mechanism by which pathogens with complex LPS extensions efficiently evade a first-line mucosal innate immune defense. The structure also reveals for the first time the dominant form of anhydro-Kdo.
authors.affiliation: University of Southampton, Department of Child Health, Division of Clinical and Experimental Sciences, Faculty of Medicine, Sir Henry Wellcome Laboratories, Southampton General Hospital, Southampton, United Kingdom.|Institute for Life Sciences, University of Southampton, Southampton, United Kingdom.|National Institute for Health Research, Southampton Respiratory Biomedical Research Unit, Southampton Centre for Biomedical Research, University Hospital Southampton NHS Foundation Trust, Southampton, United Kingdom.
authors.forename: Howard W
authors.initials: HW
authors.lastname: Clark
authors.affiliation: University of Southampton, Department of Child Health, Division of Clinical and Experimental Sciences, Faculty of Medicine, Sir Henry Wellcome Laboratories, Southampton General Hospital, Southampton, United Kingdom.
authors.forename: Rose-Marie
authors.initials: RM
authors.lastname: Mackay
authors.affiliation: Mammalian Genetics Unit, MRC Harwell, Harwell Science & Innovation Campus, Oxfordshire, United Kingdom.
authors.forename: Mary E
authors.initials: ME
authors.lastname: Deadman
authors.affiliation: Mammalian Genetics Unit, MRC Harwell, Harwell Science & Innovation Campus, Oxfordshire, United Kingdom.
authors.forename: Derek W
authors.initials: DW
authors.lastname: Hood
authors.affiliation: University of Southampton, Department of Child Health, Division of Clinical and Experimental Sciences, Faculty of Medicine, Sir Henry Wellcome Laboratories, Southampton General Hospital, Southampton, United Kingdom.|Institute for Life Sciences, University of Southampton, Southampton, United Kingdom.|National Institute for Health Research, Southampton Respiratory Biomedical Research Unit, Southampton Centre for Biomedical Research, University Hospital Southampton NHS Foundation Trust, Southampton, United Kingdom.
authors.forename: Jens
authors.initials: J
authors.lastname: Madsen
authors.affiliation: University of Oxford, Department of Paediatrics, John Radcliffe Hospital, Oxford, United Kingdom.
authors.forename: E Richard
authors.initials: ER
authors.lastname: Moxon
authors.affiliation: National Institute for Health Research, Southampton Respiratory Biomedical Research Unit, Southampton Centre for Biomedical Research, University Hospital Southampton NHS Foundation Trust, Southampton, United Kingdom.
authors.forename: J Paul
authors.initials: JP
authors.lastname: Townsend
authors.affiliation: MRC Immunochemistry Unit, Department of Biochemistry, University of Oxford, Oxford, United Kingdom.
authors.forename: Kenneth B M
authors.initials: KBM
authors.lastname: Reid
authors.affiliation: School of Life Sciences, Keele University, Staffordshire, United Kingdom.
authors.forename: Abdul
authors.initials: A
authors.lastname: Ahmed
authors.affiliation: School of Life Sciences, Keele University, Staffordshire, United Kingdom.
authors.forename: Amy J
authors.initials: AJ
authors.lastname: Shaw
authors.affiliation: School of Life Sciences, Keele University, Staffordshire, United Kingdom.
authors.forename: Trevor J
authors.initials: TJ
authors.lastname: Greenhough
authors.affiliation: School of Life Sciences, Keele University, Staffordshire, United Kingdom a.k.shrive@keele.ac.uk.
authors.forename: Annette K
authors.initials: AK
authors.lastname: Shrive
mesh_terms: D018360:Crystallography, X-Ray; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D006193:Haemophilus influenzae / Q000737:chemistry*; D006801:Humans; D008070:Lipopolysaccharides / Q000737:chemistry* / Q000378:metabolism; D011485:Protein Binding; D037663:Pulmonary Surfactant-Associated Protein D / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
chemical_list: D008070:Lipopolysaccharides; D037663:Pulmonary Surfactant-Associated Protein D; D011994:Recombinant Proteins