Glycobiology Advance Access first published online on December 15, 2004
This version published online on December 21, 2004
Glycobiology, doi:10.1093/glycob/cwi022
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1 Institute for Reproductive Medicine, School of Veterinary Medicine Hannover, Foundation, Bünteweg 15, 30559 Hannover, Germany
* To whom correspondence should be addressed. The mammalian oocyte is encased by a transparent extracellular matrix, the zona pellucida, which consists of three glycoproteins ZPA, ZPB and ZPC. The glycan structures of the porcine zona pellucida and the complete N-glycosylation pattern of the ZPB/ZPC oligomer has been recently described. Here we report the N-glycan pattern and N-glycosylation sites of the porcine zona pellucida glycoprotein ZPA of an immature oocyte population as determined by a mass spectrometric approach. Ingel deglycosylation of the electrophoretically separated ZPA protein and comparison of the pattern obtained from the native, the desialylated and the endo-ßgalactosidase-treated glycoprotein allowed the assignment of the glycan structures by MALDI-ToF-MS by considering the reported oligosaccharide structures. The major N-glycans are neutral bi-antennary complex structures containing one or two terminal galactose residues. Complex N-glycans carrying N-acetyllactosamine repeats are minor components and are mostly sialylated. A significant signal corresponding to a high-mannose type chain appeared in the three glycan maps. MS-MS analysis confirmed its identity as a pentamannosyl N-glycan. By the combination of tryptic digestion of the endo-ß-galactosidase-treated ZP glycoprotein mixture and in-gel digestion of ZPA with lectin-affinity chromatography and reverse-phase HPLC five of six N-glycosylation sites at Asn84/93, Asn268, Asn316, Asn323 and Asn530 were identified by MS. Only one sites was found to be glycosylated in the N-terminal tryptic glycopeptide with Asn84/93. N-glycosidase F treatment of the isolated glycopeptides and MS analysis resulted in the identification of the corresponding deglycosylated peptides.
Received August 27, 2004
Revised November 30, 2004
Accepted December 4, 2004
Article
Analysis of N-linked glycans of porcine zona pellucida glycoprotein ZPA by MALDI-ToF mass spectrometry: a contribution to understanding zona pellucida structure
2 Shimadzu Deutschland GmbH, Albert-Hahn-Str. 6-10, 47269 Duisburg, Germany
3 Institute for Animal Breeding, Hoeltystr. 10, 31535 Neustadt, Germany
4 Department of Gynaecology and Obstetrics, Georg August University of Göttingen, Robert-Koch-Str. 40, 37075 Göttingen, Germany
Edda Töpfer-Petersen, E-mail: Edda.Toepfer-Petersen{at}tiho-hannover.de
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