Evidence for a novel O-linked sialylated trisaccharide on Ser-248 of human plasminogen 2

S R Pirie-Shepherd, R D Stevens, N L Andon, J J Enghild, S V Pizzo

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    Abstract

    Human plasminogen, the inactive precursor of plasmin, exists in two major glycoforms. Plasminogen 1 contains an N-linked oligosaccharide at Asn-289 and an O-linked oligosaccharide at Thr-345. Plasminogen 2 is known to contain only an O-linked oligosaccharide at Thr-345. However, plasminogen 2 displays a further well documented microheterogeneity dependent on the N-acetylneuraminic acid content, which has functional consequences with regard to activation of plasminogen. The proposed structure and number of known oligosaccharide linkages in plasminogen 2 is insufficient to account for this microheterogeneity. In the present study, a combination of trypsin digestion, lectin affinity chromatography, Edman degradation amino acid sequence analysis, carbohydrate composition analysis, and mass spectrometry revealed the existence of a novel site for O-linked glycosylation on plasminogen 2 at Ser-248. Direct evidence for the structure of the carbohydrate was obtained from a combination of lectin affinity chromatography, desialylation experiments, and mass spectrometry analysis. These findings provide a structural basis for some of the observed microheterogeneity, and have implications with regard to the known functional consequences of the extent of sialylation of plasminogen.
    Original languageEnglish
    JournalJournal of Biological Chemistry
    Volume272
    Issue11
    Pages (from-to)7408-11
    Number of pages3
    ISSN0021-9258
    Publication statusPublished - 1997

    Keywords

    • Amino Acid Sequence
    • Chromatography, High Pressure Liquid
    • Glycosylation
    • Humans
    • Molecular Sequence Data
    • Plasminogen
    • Trisaccharides

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