The sperm agglutination antigen-1 (SAGA-1) glycoforms of CD52 are O-glycosylated

Author: Parry Simon   Wong Nyet-Kui   Easton Richard L   Panico Maria   Haslam Stuart M   Morris Howard R   Anderson Peggy   Klotz Kenneth L   Herr John C   Diekman Alan B   Dell Anne  

Publisher: Oxford University Press

ISSN: 1460-2423

Source: Glycobiology, Vol.17, Iss.10, 2007-10, pp. : 1120-1126

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Abstract

CD52 is composed of a 12 amino acid peptide with N-linked glycans bound to the single potential glycosylation site at position 3, and a glycosylphosphatidylinositol-anchor attached at the C-terminus. Some glycoforms of this molecule expressed in the male reproductive tract are recognized by complement-dependent sperm-immobilizing antibodies in infertile patients making this antigen an important target for immunocontraception and fertility studies. Although the amount of posttranslational modification is already remarkable for such a small polypeptide, O-glycosylation of CD52 has additionally been implicated by several studies, but never rigorously characterized. In this report, we show clear evidence for the presence of O-glycans in CD52 preparations immunopurified using the murine S19 monoclonal antibody generated against sperm agglutination antigen-1 (SAGA-1), a male reproductive tract specific form of CD52. The O-glycans have been characterized by MALDI-TOF and tandem mass spectrometry after reductive elimination and permethylation. The data indicate that the major SAGA-1 O-glycans are core 1 and 2 mucin-type structures, with and without sialic acid (NeuAc02Hex13HexNAc12HexNAcitol). Minor fucosy- lated O-glycans are also present including some struc- tures with putative Ley epitopes (NeuAc01Fuc13Hex12 HexNAc01HexNAcitol). Analysis of O-glycopeptides by tandem mass spectrometry provided an additional level of support for the O-glycosylation of SAGA-1. Elucidation of the O-glycosylation of SAGA-1 adds to the complexity of this molecule and may help to explain its biological activity.

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