Egg surface glycoprotein receptor for sea urchin sperm bindin.

Abstract

Bindin is an insoluble protein coating the sperm acrosome process and mediating the adhesion of sperm to sea urchin [Strongylocentrotus purpuratus] eggs. Milligrams of bindin were isolated. The identification, isolation and partial characterization of a high molecular weight, trypsin-sensitive glycoprotein fraction from the sea urchin egg surface having species-specific affinity for bindin, is reported. This glycoprotein may be the egg surface receptor for bindin. The bindin receptor was released from 125I-labeled eggs by parthenogenetic activation of eggs with ionophore A23187 in the presence of soybean trypsin inhibitor. The receptor has an isoelectric point of 4.02 and a MW in sea water .gtoreq. 5 .times. 106, suggesting that it is an aggregate. It contains 34% neutral sugars, which are galactose and mannose.