Isolation and characterization of proteolytic fragments of the sea urchin sperm receptor that retain species specificity

Identification of sulfated oligosialic acid units in theO-linked glycan of the sea urchin egg receptor for sperm

“…In addition, it was shown that the O-linked oligosaccharide chains labeled at their reducing terminus by reduction with [ 3 H]NaBH 4 , bound to acrosome-reacted, but not unreacted sperm. Both the inhibition and the binding processes occurred without species specificity, as expected based on earlier studies (2,(7)(8)(9). More recently, it has been shown that coupling these chains to proteins produced neoglycoproteins that inhibited fertilization; the inhibition was proportional to the valency of the oligosaccharide in the neoglycoprotein (14).…”

“…Early studies implicated not only the polypeptide backbone of the receptor, but the carbohydrate chains as well, in the sperm binding process (8,9). More recently it has been shown that sulfated O-linked glycan chains isolated from the receptor by hydrazinolysis competitively inhibit fertilization in a competition bioassay (13).…”

“…In the case of the sea urchin, earlier studies showed that the sperm protein, bindin, which is a component of the acrosome granule, plays a key role in gamete recognition (3,4). Following early work in which a high molecular weight glycoprotein on the egg cell surface was implicated as a receptor for sperm (5)(6)(7), it was shown that Pronase-generated glycopeptides prepared from this crude receptor preparation inhibited fertilization, but without species specificity (8,9). Later, a cell surface glycoprotein with a molecular mass of 350 kDa was identified as the egg receptor in Strongylocentrotus purpuratus (10,11).…”

The Involvement of the Oligosaccharide Chains of Glycoproteins in Gamete Interactions at Fertilization

“…However, as with the crude binding protein, the small glycopeptides generated by the treatment of the purified sperm binding protein with Pronase, although retaining inhibitory activity, lost species specificity [ 36, 541. When a tryptic peptide was prepared the longer glycopeptides produced retained species specificity, whereas the shorter glycopeptides although active, lacked species specificity [55]. As discussed earlier in the case of S. purpuratus, by use of bacterially expressed recombinant sperm binding protein it became clear that the polypeptide has two sperm binding domains: a non-specific binding domain and a genus-specific binding domain [41].…”

Identification of the sea urchin egg receptor for sperm using an antiserum raised against a fragment of its extracellular domain.

“…An alternative approach that was taken was the preparation of extracellular, proteolytic fragments of putative receptors on the surface of the egg . Tryptic digestion of egg surfaces rendered the eggs unable to bind sperm and the resulting digested material was found to contain proteolytic fragments that bound to homotypic sperm and inhibited fertilization in a sensitive bioassay (Schmell et al, 1977;Ruiz-Bravo and Lennarz, 1986) . In addition, such tryptic fragments were also shown to block bindin-mediated agglutination of eggs (Vacquier and Moy, 1977).…”