Structural characterization of human and bovine lung surfactant protein D.
Human and bovine surfactant proteins D (SP-D) were purified from late amniotic fluid and bronchioalveolar lavage on the basis of its Ca(2+)-dependent affinity for maltose. The molecular mass of a trimeric subunit was determined by matrix-assisted laser desorption ionization MS to lie in the range 115-125 kDa for human SP-D and 110-123 kDa for bovine SP-D. A single polypeptide chain was determined at 37-41 and 36-40 kDa for the human and bovine species respectively. The major parts of the primary structures of both SP-D molecules were determined by a combination of MS and Edman degradation. The heterogeneity in SP-D was caused mainly by a high number of post-translational modifications in the collagen-like region. Proline and lysine residues were partly hydroxylated and lysine residues were further O-glycosylated with the disaccharide galactose-glucose. A partly occupied N-linked glycosylation site was characterized in human SP-D. The carbohydrate was determined as a complex type bi-antennary structure, with a small content of mono-antennary and tri-antennary structures. No sialic acid residues were present on the glycan, but some had an attached fucose and/or an N-acetylglucosamine residue linked to the core. Bovine SP-D was determined as having a similar structure.
Leth-Larsen
R
R
Institute of Molecular Biology, University of Southern Denmark, Odense University, DK-5000 Odense, Denmark.
Holmskov
U
U
Højrup
P
P
D000595:Amino Acid Sequence; D000653:Amniotic Fluid / Q000737:chemistry*; D000818:Animals; D001992:Bronchoalveolar Lavage Fluid / Q000737:chemistry*; D002352:Carrier Proteins / Q000737:chemistry; D002417:Cattle; D002851:Chromatography, High Pressure Liquid; D017364:Collagenases; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D006023:Glycoproteins / Q000737:chemistry* / Q000302:isolation & purification; D006031:Glycosylation; D006801:Humans; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010084:Oxidation-Reduction; D010446:Peptide Fragments / Q000737:chemistry; D011247:Pregnancy; D037663:Pulmonary Surfactant-Associated Protein D; D011663:Pulmonary Surfactants / Q000737:chemistry* / Q000302:isolation & purification; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D014357:Trypsin
D002352:Carrier Proteins; D006023:Glycoproteins; D010446:Peptide Fragments; D037663:Pulmonary Surfactant-Associated Protein D; D011663:Pulmonary Surfactants; D014357:Trypsin; D017364:Collagenases