Structure of the O-glycopeptides isolated from bovine milk component PP3.
The heat-stable acid-soluble phosphoglycoprotein component PP3 was isolated from the bovine milk proteose peptone fraction by concanavalin A affinity chromatography. Glycopeptides from the ConA-bound fraction corresponding to the component PP3 were obtained by Pronase digestion and were separated by gel filtration into high and low-molecular-mass glycopeptides. In a previous work, we have investigated the structure of the N-glycans from the high-molecular-mass glycopeptides [Girardet et al. (1995) Eur J Biochem 234: 939-46]. Here, we describe the structure of the O-glycans from the low-molecular-mass glycopeptides. By combining methylation analysis, mass spectrometry, 400 MHz 1H-NMR spectroscopy and peptide sequence analysis, we show that the low-molecular-mass fraction contains several neutral glycopeptides. A mixture of the following three glycan structures linked to the Thr86 has been identified: GalNac alpha1-O-Thr, Gal(beta1-3)GalNAc alpha1-O-Thr and Gal(beta1-4)GlcNAc(beta1-6)[Gal(beta1-3)]GalNAc alpha1-O-Thr.
Coddeville
B
B
Laboratoire de Chimie Biologique, Unité Mixte de Recherche du Centre National de la Recherche Scientifique no 111, Université des Sciences et Technologies de Lille, Villeneuve d'Ascq, France.
Girardet
J M
JM
Plancke
Y
Y
Campagna
S
S
Linden
G
G
Spik
G
G
D000595:Amino Acid Sequence; D000818:Animals; D002240:Carbohydrate Sequence; D002364:Caseins / Q000737:chemistry*; D002417:Cattle; D002852:Chromatography, Ion Exchange; D005260:Female; D006020:Glycopeptides / Q000737:chemistry* / Q000302:isolation & purification; D006023:Glycoproteins / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D015394:Molecular Structure; D008970:Molecular Weight; D009844:Oligosaccharides / Q000737:chemistry / Q000302:isolation & purification; D010446:Peptide Fragments / Q000737:chemistry*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
D002364:Caseins; D006020:Glycopeptides; D006023:Glycoproteins; D009844:Oligosaccharides; C085522:PP3 protein, Bos taurus; D010446:Peptide Fragments