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Isolation, composition, and biological activity of sugar chains of porcine oocyte zona pellucida 55K glycoproteins
Author(s) -
Yurewicz Edward C.,
Pack Beverley A.,
Sacco Anthony G.
Publication year - 1991
Publication title -
molecular reproduction and development
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.745
H-Index - 105
eISSN - 1098-2795
pISSN - 1040-452X
DOI - 10.1002/mrd.1080300209
Subject(s) - zona pellucida , zona pellucida glycoprotein , glycan , glycoprotein , population , chitobiose , biochemistry , biology , sephadex , sperm , oocyte , oligosaccharide , chemistry , enzyme , microbiology and biotechnology , embryo , botany , demography , chitin , sociology , chitosan
ZP3, a preparation of the 55K families of porcine oocyte zona pellucida, possesses carbohydrate‐dependent ligand activity for boar sperm. The aim of the present study was to analyze ZP3 N‐ and O‐linked oligosaccharides with respect to size distribution, composition, and role in sperm‐zona recognition events. Digestion of denatured ZP3 with peptide N‐glycosidase F (PNGaseF) released the majority of N‐glycans which fractionated on Sephadex G‐75 resin as a polydisperse population with apparent molecular masses ranging from 1,900–8,200 Da. The higher molecular weight N‐glycans were characterized by the presence of strongly anionic sulfated/sialylated polylactosamine structures. Alkaline‐borohydride treatment of the PNGaseF‐digested core proteins liberated O‐glycans as a heterogeneous population of oligosaccharide alcohols, which were fractionated on a Sephadex G‐50 column. Compositional analyses indicated sulfated polylactosamine units associated with the higher molecular weight O‐glycans. Preincubation of boar sperm with ZP3 or purified O‐glycans, but not N‐glycans, inhibited subsequent attachment to zona‐encased oocytes. Purified O‐glycans were, however, 2 to 3 orders of magnitude less effective than ZP3 as competitive ligands. The results document the extreme heterogeneity of the ZP3 carbohydrate moiety, in large part attributable to a board spectrum of variably sized N‐ and O‐linked sulfated polylactosamines. Ligand competition bioassays suggest that O‐glycans mediate, at least in part, the sperm adhesive properties of ZP3 and strongly imply that high‐affinity interaction of ZP3 sugar chains with complementary sperm receptors is dependent upon their covalent association with core proteins.