title: Characterization of glycoprotein PAS-6/7 from membranes of bovine milk fat globules.
abstract: Glycoprotein components PAS-6 and PAS-7 were purified from bovine milk-fat-globule membranes and the amino acid sequence of their common polypeptide core, PAS-6/7, was determined by peptide and cDNA sequencing. The cDNA encoded a signal peptide of 18 amino acid residues and a mature PAS-6/ 7 protein of 409 amino acid residues. A cDNA splice variant was identified by reverse transcription/ PCR. Results obtained by amino acid analyses, amino-acid-sequence analyses, carbohydrate-composition determinations, and MS analyses of glycopeptides revealed that both proteins were glycosylated with a carbohydrate structure that contained galactose, N-acetylgalactosamine and fucose, and which was O-linked to Ser9 in PAS-6 and to Thr16 in PAS-7. In addition, PAS-6 and PAS-7 were N-glycosylated at Asn41 with a hybrid-type-carbohydrate structure. A high-mannose glycan was N-linked to Asn209 of PAS-6. The sequence of PAS-6/7 contained two epidermal growth factor (EGF)-like domains in the N-terminal region, the second of which contained an RGD cell-adhesion sequence in an extended loop. The EGF-like domains were followed by a C-terminal tandem repeat, which showed 60-63% similarity to the C1-C2 domain of blood-clotting factors V and VIII. The disulfide bonds within the C1-C2 domain were identified.
authors.affiliation: Protein Chemistry Laboratory, University of Aarhus, Denmark.
authors.forename: J
authors.initials: J
authors.lastname: Hvarregaard
authors.forename: M H
authors.initials: MH
authors.lastname: Andersen
authors.forename: L
authors.initials: L
authors.lastname: Berglund
authors.forename: J T
authors.initials: JT
authors.lastname: Rasmussen
authors.forename: T E
authors.initials: TE
authors.lastname: Petersen
mesh_terms: D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002241:Carbohydrates / Q000032:analysis; D002417:Cattle; D018076:DNA, Complementary / Q000235:genetics; D004220:Disulfides / Q000737:chemistry; D005260:Female; D006020:Glycopeptides / Q000737:chemistry / Q000235:genetics; D006031:Glycosylation; D008562:Membrane Glycoproteins / Q000737:chemistry* / Q000235:genetics; D008894:Milk Proteins / Q000737:chemistry* / Q000235:genetics; D008969:Molecular Sequence Data; D015394:Molecular Structure; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
chemical_list: D002241:Carbohydrates; D018076:DNA, Complementary; D004220:Disulfides; D006020:Glycopeptides; D008562:Membrane Glycoproteins; D008894:Milk Proteins