Dephosphorylation of sea urchin sperm guanylate cyclase during fertilization

Exposure of Arbacia punctulata spermatozoa to solubilized egg jelly results in the immediate dephosphorylation (within 3 sec) of an abundant 160,000 dalton (160 kDa) sperm membrane protein, and a simultaneous increase in its electrophoretic mobility to 150 kDa. The sperm phosphoprotein has been identified as guanylate cyclase. Correlated with the mobility shift of the cyclase is a decrease in its enzymatic activity. In this paper we will briefly review the work on the sperm guanylate cyclase, present new data on the role of ion fluxes in the control of its dephosphorylation, and discuss what role the dephosphorylation might play in successful sperm-egg interaction.