Complementarity between sperm surface β-l,4-galactosyl-transferase and egg-coat ZP3 mediates sperm–egg binding

Abstract

Despite its importance, the molecular basis of mammalian gamete recognition has remained unclear. The enzyme beta-1,4-galactosyltransferase (Gal-transferase) has been viewed traditionally as a biosynthetic component of the Golgi complex, but is also found on the surface of many cells where it can bind its specific glycoside substrate on adjacent cell surfaces or in the extracellular matrix. In mouse it has been suggested that Gal-transferase on the sperm head mediates fertilization by binding oligosaccharide residues in the egg coat, or zona pellucida, and that the ability of the zona pellucida to bind sperm is conferred by oligosaccharides of the ZP3 glycoprotein. However, it has not been confirmed that Gal-transferase and ZP3 are in fact complementary gamete receptors whose interaction mediates sperm-egg binding. Here we show that mouse sperm Gal-transferase specifically recognizes those oligosaccharides on ZP3 that have sperm-binding activity, but does not interact with other zona pellucida glycoproteins. In contrast, all zona pellucida glycoproteins are recognized by non-sperm Gal-transferase, demonstrating a more stringent substrate specificity for the sperm enzyme. This interaction is required for sperm-egg binding because blocking or removing the binding site for Gal-transferase on ZP3 inhibits its ability to bind sperm. After the release of the sperm acrosome, the transferase relocalizes to a new membrane domain where it can no longer bind to ZP3, which is consistent with the inability of acrosome-reacted sperm to bind ZP3 or to initiate binding to the zona pellucida. Following fertilization, ZP3 is modified by egg cortical granule secretions so that it loses sperm receptor activity, which can be accounted for by a selective loss of its binding site for sperm Gal-transferase. These results show that sperm surface beta-1,4-galactosyltransferase and the egg-coat glycoprotein ZP3 are complementary adhesion molecules that mediate primary gamete binding in the mouse.

Binding of Zona Binding Inhibitory Factor-1 (ZIF-1) from Human Follicular Fluid on Spermatozoa

“…There is compelling evidence that carbohydratebinding proteins on the sperm surface mediate gamete recognition of different species by binding with high affinity and specificity to complex glycoconjugates on the zona pellucida (14 -16, 19, 34), including human (16,19,35,36). In the past two decades, the presence of several carbohydrate-binding proteins, such as galactosyltransferase (37), fucosyltransferase (38), ␣-mannosidase (39, 40), fucose-binding protein (41), selectin-like molecules (42), ␤-hexosaminidase (43), FA-1 (44), and others, on the sperm plasma membrane and their complementary sugar molecules on the zona pellucida have been suggested to be involved in sperm-egg interaction.…”

Localization of carbohydrate chains of pig sperm ligand in the glycoprotein ZPB of egg zona pellucida

“…In this study, we tried to isolate three glycopeptides, having bohydrate chains of ZPC [1,7]. However, carbohydrate strucone Asn residue, to which the intact carbohydrate chain is …”

“…When N-acetyllactosamine repeats in the non-reducing regions of carbohydrate chains of removed in the secretory pathway, and mature ZPB consists of 330 amino acid residues [9]. Recently, we have reported that the ZPB and ZPC are removed by digestion with endo-β-galactosidase, they become separable by reverse-phase HPLC [5].N-terminal fragment (amino acid residues 137Ϫ247) obtained by lysyl endopeptidase digestion of endo-β-galactosidaseϪdi-In mice, sperm bind to A-galactose residues and/or β-N-acetylglucosamine residues at the non-reducing end of O-linked car-gested ZPB inhibits sperm-egg binding [10].In this study, we tried to isolate three glycopeptides, having bohydrate chains of ZPC [1,7]. However, carbohydrate strucone Asn residue, to which the intact carbohydrate chain is …”

A Novel On‐Chip Method for Differential Extraction of Sperm in Forensic Cases

“…This oligosaccharide sequence has been reported as a major contributing element for human sperm‐oocyte binding 22, 23. There are also components on the sperm membrane reported as docking units, including the β1–4 galactosyltransferase 1 (B4GAL‐T1) peripheral protein, which plays a crucial role in human sperm‐oocyte binding 24, 25, 26, 27, 28, 29. To understand the dynamics of SLeX binding to sperm surface, we used B4GAL‐T1 as a model docking/binding unit on the sperm membrane and computed a molecular docking simulation to discover the locations and energetics of binding ( Figure   2 ).…”