CHARGE INTERACTIONS IN SPERM-EGG RECOGNITION

A novel method using derivatized agarose beads for investigating the t ypes of molecules, when isolated from all others, that can form stable adhesive bonds, was recently described by Rogue et al. (1996). The fi ndings from this study were extended to living sea urchin cell systems . Both the bead results and the experiments with sea urchin cells sugg ested that phosphorylated amino acids can form stable adhesive bonds w ith positively charged peptides (Rogue et al., 1996). As these experim ents only examined phosphorylated amino acids, the validity of the hyp otheses developed in the earlier study was dependent on extending the experiments to additional phosphorylated molecules In this study, effe cts of D-mannose, D-mannose-1-phosphate, D-fructose, D-fructose-1-phos phate, maltose and maltose-1-phosphate on embryo cell reaggregation an d sperm-egg interaction using untreated, jelly coat-free and vitelline layer disrupted Strongylocentrotus purpuratus sea urchin eggs were ex amined. The phosphorylated sugars (50 mM), and not their non-phosphory lated counterparts, strongly inhibited fertilization of the 3 types of eggs. ATP, at concentrations as low as 0.8 mM also completely inhibit ed fertilization. The phosphorylated sugars had little or no effect on reaggregating sea urchin blastula cells. A likely explanation of thes e results is that sperm-egg interaction in the sea urchin involves pos itively and negatively charged receptors; the positively charged recep tors are blocked by exogenously added phosphorylated molecules. These and earlier studies indicate that by extending results from bead model ing studies to living systems, interesting information can be obtained regarding bonding mechanisms that may modulate adhesive interactions.