Asparagine-linked carbohydrate chains of inducible rat parotid proline-rich glycoprotein contain terminalβ-linked N-acetylgalactosamine |
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Authors: | Gurrinder S Bedi |
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Institution: | (1) Department of Microbiology and Immunology, Philadelphia, PA and Magainin Pharmaceuticals, Inc. Plymouth Meeting, The Medical College of Pennsylvania, PA, USA |
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Abstract: | Rats treated with daily injection of DL-isoproterenol for 10 consecutive days (25 mg kg1 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.
This revised version was published online in August 2006 with corrections to the Cover Date. |
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Keywords: | Parotid salivary proline-rich protein inducible glycoprotein asparagine-linked carbohydrate N-acetylgalactosamine isoproterenol |
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