Specific in vitro interaction between recombinant Strongylocentrotus purpuratus bindin and a recombinant 45A fragment of the putative bindin receptor.

The interaction between recombinant Strongylocentrotus purpuratus sperm bindin and a recombinant fragment of the putative egg bindin receptor of the same species was measured in vitro. In solution these molecules interact with simple bimolecular kinetics, displaying an equilibrium dissociation constant of about 0.1 microM. Thus, as implied by many observations in vivo and in vitro, bindin and the putative egg receptor display a specific affinity for one another.