Studies on the carbohydrate-binding characteristics of human pulmonary surfactant-associated protein A and comparison with two other collectins: mannan-binding protein and conglutinin

J S Haurum, S Thiel, H P Haagsman, S B Laursen, B Larsen, J C Jensenius

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    Abstract

    The surfactant-associated protein A (SP-A) belongs to the collectin family, a group of C-type lectins encompassing also surfactant-associated protein D, mannan-binding protein (MBP) and conglutinin. These proteins all have carbohydrate-recognition domains joined to collagen stalks. It seems likely that SP-A, like MBP and conglutinin, may mediate anti-microbial activity through binding to carbohydrates on the microorganisms and collectin receptors on phagocytic cells. We have studied the influence of carbohydrates on the binding of SP-A, MBP and conglutinin to mannan in an enzyme-linked lectin-binding assay. All sugars were of D-configuration, except fucose of which both L- and D-configurations were tested. The order of inhibiting potency on the binding of SP-A was: N-acetylmannosamine > L-fucose, maltose > glucose > mannose. The following sugars were non-inhibitory: galactose, D-fucose, glucosamine, mannosamine, galactosamine, N-acetylglucosamine, and N-acetylgalactosamine. The best inhibitor of MBP was N-acetylglucosamine. Otherwise MBP showed a selectivity similar to that of SP-A. Conglutinin binding was inhibited by all the sugars examined except N-acetylgalactosamine. For conglutinin, as for MBP, the best inhibitor was N-acetylglucosamine. Normal human SP-A, alveolar-proteinosis SP-A purified by ion-exchange chromatography, and alveolar-proteinosis SP-A purified by n-butanol extraction showed no difference in sugar selectivity. The influence of pH and of the calcium concentration was also examined. Organic solvent-extracted SP-A from patients suffering from alveolar proteinosis and normal SP-A showed different sensitivity profiles.
    Original languageEnglish
    JournalBiochemical Journal
    Volume293 ( Pt 3)
    Pages (from-to)873-8
    Number of pages6
    ISSN0264-6021
    Publication statusPublished - 1 Aug 1993

    Keywords

    • Antibody Specificity
    • Binding Sites
    • Carbohydrate Metabolism
    • Carrier Proteins
    • Collectins
    • Glycoproteins
    • Humans
    • Hydrogen-Ion Concentration
    • Lectins
    • Proteolipids
    • Pulmonary Surfactant-Associated Protein A
    • Pulmonary Surfactant-Associated Proteins
    • Pulmonary Surfactants
    • Serum Globulins

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