Structure and function of sea urchin egg jelly molecules

Abstract

Sea urchin egg jelly consists of a fucose sulfate glycoconjugate, a sialoglycoprotein and sperm-activiting peptides. The fucose sulfate glycoconjugate isolated from the solubilized jelly layer of Hemicentrotus pulcherrimus is composed of several proteins (a sugar-containing core protein, a 258 kDa protein, a 237 kDa protein and a 120 kDa protein); the substance plays a major role in the inducetion of the acrosome reaction in Hemicentrotus pulcherrimus spermatozoa. The protein components of the fucose sulfate glycoconjugate seem to be associated with one another through disulfide bonds. Sixty-three sperm-activating peptides have been isolated from the solubilized jelly layers of fifteen sea urchin species distributed over four taxonomic orders. Sperm-activating peptides stimulate sperm respiraton and motility, increase the levels of both CAMP and CGMP in sea urchin sperm cells, induce net H+ efflux from sea urchin spermatozoa and cause a shift in the mobility of guanylate cyclase, a major sperrn plasma protein, on an SDS-polyacrylamide gel. These peptides are specific at the ordinal level and are classified into four groups, i.e., sperm-activating peptide I (SAP-I), sperm-activating peptide II (SAP-II), sperm-activating peptide III (SAP-III) and sperm-activating peptide IV (SAP-IV). SAP-I (Gly-Phe-Asp-Leu-Asn-Gly-Gly-Gly-Val-Gly) promotes the induction of the acrosome reaction in Hemicentrotus pulcherrimus spermatozoa by acting as a specific co-factor of the fucose sulfate glycoconjugate.