CARBODIIMIDE-INDUCED LABELING OF SEA-URCHIN SURFACES (ECHINOIDEA, ECHINODERMATA)

A method for radiolabelling echinoderm body surfaces, using water-soluble carbodiimide was developed. The number of carboxyl groups reacting with carbodiimide was estimated as 20 to 30 nmole g(-1) dry weight of sea urchin spines. There were no phosphate groups accessible to carbodiimide on the surface coat. Several enzymes were used to release bound radiolabel from the spines labelled with carbodiimide and radioactive amino acid, Results obtained with proteases and hyaluronidase showed that radiolabel was bound to the glycoprotein and/or protein molecules on the extracellular surface of the spine epidermis.