Asparagine-linked carbohydrate chains of inducible rat parotid proline-rich glycoprotein contain terminal beta-linked N-acetylgalactosamine.
Rats treated with daily injection of DL-isoproterenol for 10 consecutive days (25 mg kg(-1) body weight) showed marked induction of a proline-rich glycoprotein (GPRP) of 220 kDa. Proteinase K digestion of GPRP produced a homogeneous glycopeptide with an average chemical composition as follows (residues per mol): Pro4, Glx3, Asx2, Gly1, His1, Thr1, Arg1, GlcNAc5, GalNac1, Man3, Gal2-3, and Fuc1. The structural analysis of the asparagine-linked carbohydrate unit was performed by methylation, periodate oxidation and enzymatic degradation. Methylation studies indicated that the three mannosyl residues were substituted at 1,2-, 1,2,4-, and 1,3,6-positions. Fucose, N-acetylgalactosamine, 1.5 residues of galactose and 0.35 residues of N-acetylglucosamine were terminally located and one galactose residue was 1,4-substituted. Approximately four of the 5 N-acetylglucosamine residues were substituted at 1,4-position and approximately 1 residue of N-acetylglucosamine was substituted at 1,4,6-positions. Periodate oxidation studies and exoglycosidase results were consistent with the methylation data. Based on the results of Smith degradation, methylation and sequential exoglycosidase digestions a triantennary oligosaccharide structure having terminal N-acetylgalactosamine in one of the branches is proposed for the major Asn-linked carbohydrate moiety of GPRP.
Bedi
G S
GS
The Medical College of Pennsylvania, Department of Microbiology and Immunology, Philadelphia, USA. Bedi@allegheny.edu
D000818:Animals; D001216:Asparagine / Q000737:chemistry; D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D002241:Carbohydrates / Q000737:chemistry; D008401:Gas Chromatography-Mass Spectrometry; D007545:Isoproterenol / Q000494:pharmacology; D008969:Molecular Sequence Data; D009844:Oligosaccharides / Q000737:chemistry; D010306:Parotid Gland / Q000737:chemistry* / Q000187:drug effects / Q000378:metabolism; D010452:Peptide Biosynthesis / Q000187:drug effects; D010455:Peptides / Q000737:chemistry*; D055232:Proline-Rich Protein Domains; D051381:Rats
D002241:Carbohydrates; D009844:Oligosaccharides; D010455:Peptides; D001216:Asparagine; D007545:Isoproterenol