ABSTRACT
Sea urchin egg jelly consists of a fucose sulfate glycoconjugate (FSG), a sialoglycoprotein and sperm-activating peptides (SAPs). FSG induces the acrosome reaction of sea urchin spermatozoa, and sperm-activating peptide I (SAP-I: Gly- Phe-Asp-Leu-Asn-Gly-Gly-Gly-Val-Gly) promotes the acrosome reaction as a specific co-factor of FSG. We isolated FSG from the egg jelly of four species of sea urchins, Hemicentrotus pulcherrimus, Pseudocentrotus depressus, Strongylocentrotus nudus and Anthocidaris crassispina. FSG from H. pulcherrimus possessed protein about two times more than fucose by weight. The protein/fucose ratio was about 0.5, 0.5, and 1.0 for FSG from P. depressus, S. nudus and A. crassispina, respectively. When FSGs from four species were analyzed by SDS-polyacrylamide gel electrophoresis under reduced conditions, they showed two major similar protein bands. However, polyclonal rabbit or mouse antibody raised against H. pulcherrimus FSG did not react with FSGs from other three species when they were examined by double diffusion test (Ouchterlony) and electroimmunoblotting. Among FSGs obtained from P. depress, S. nudus and A. crassispina tested, only FSG from P. depressus induced partially the acrosome reaction of H. pulcherrimus spermatozoa although it required about five times higher concentration of FSG than that of H. pulcherrimus. SAP-I promoted the rates of the acrosome reaction of H. pulcherrimus with FSG from P. depressus. FSGs from P. depressus, S. nudus or A. crassispina did not elevate cAMP levels in H. pulcherrimus spermatozoa.
