by W.J. Lennarz, USA

Dr. W. J. Lennarz (USA) summarized the events in gamete interaction leading to fertilization in sea urchin, frog and mouse. To identify the molecule on the cell surface of egg responsible for interacting with sperm, a proteolytic fragment (70Kd sulfated glycoprotein) released from the sea urchin egg was isolated and antiserum was raised. By using this antiserum, a cDNA clone(45A) was isolated. This clone codes for 889 amino acids without transmembrane domain and the deduced protein has some similarity with HSP 110 protein. By a biochemical approach using this antiserum to monitor the steps, the receptor protein from sea urchin eggs has been purified. This molecule was shown to be a heavily glycosylated 350kD cell surface protein and a possible model of this protein on cell surface and cortical granules of the egg is proposed. From the results of sperm binding inhibition assay by fragments of this protein and of sperm binding on beads conjugated with the fragments, a species specific binding domain of this molecule (343-586 amino acids has been identified). By assay of binding of sperm on coated beads and inhibition of the binding, gp69 and gp64 were shown to be candidates for the binding molecule in xenopus egg.

Yoshitake Nishimune, Japan