Galactose at the nonreducing terminus of O-linked oligosaccharides of mouse egg zona pellucida glycoprotein ZP3 is essential for the glycoprotein's sperm receptor activity.
During fertilization in mice, zona pellucida glycoprotein ZP3 mediates initial sperm-egg interactions by serving as receptor for sperm. Purified egg ZP3, as well as ZP3-derived O-linked oligosaccharides, exhibit sperm receptor activity in vitro. We report that treatment of purified egg ZP3 and ZP3-derived O-linked oligosaccharides with either alpha-galactosidase or galactose oxidase results in loss of sperm receptor activity. In the latter case, sperm receptor activity can be restored to the oxidized glycoprotein and O-linked oligosaccharides by treatment with sodium borohydride. We conclude that galactose, located in alpha-linkage at the nonreducing terminus of O-linked oligosaccharides, is at least one of the sugar determinants on ZP3 responsible for binding of sperm to the zona pellucida.
Bleil
J D
JD
Department of Cell and Developmental Biology, Roche Institute of Molecular Biology, Nutley, NJ 07110.
Wassarman
P M
PM
D000818:Animals; D002851:Chromatography, High Pressure Liquid; D004527:Egg Proteins; D005260:Female; D005690:Galactose / Q000494:pharmacology*; D005692:Galactose Oxidase / Q000378:metabolism; D006023:Glycoproteins / Q000032:analysis*; D006026:Glycoside Hydrolases / Q000378:metabolism; D008297:Male; D008562:Membrane Glycoproteins; D051379:Mice; D010063:Ovum / Q000032:analysis*; D011956:Receptors, Cell Surface / Q000378:metabolism*; D013084:Sperm-Ovum Interactions; D015044:Zona Pellucida / Q000032:analysis*; D000072216:Zona Pellucida Glycoproteins
D004527:Egg Proteins; D006023:Glycoproteins; D008562:Membrane Glycoproteins; D011956:Receptors, Cell Surface; D000072216:Zona Pellucida Glycoproteins; C000606521:Zp3 protein, mouse; C035027:egg surface sperm receptor; D005692:Galactose Oxidase; D006026:Glycoside Hydrolases; D005690:Galactose