Protein-protein interactions and structural entities within the sea urchin extraembryonic matrix, the hyaline layer

We have investigated the effects of a variety of experimental conditions on the structural integrity of the sea urchin extraembryonic matrix, the hyaline layer. Removal of Ca2+ resulted in the quantitative release of hyalin from isolated layers. Protein gel blot analyses indicated that, in the absence of Ca2+, hyalin was also quantitatively released from the layers surrounding 1-h-old embryos. However, no other polypeptides of the hyaline layer were released in significant amounts. The layers remaining after removal of hyalin were refractory to digestion with proteinase K and dissociated only in the presence of chaotropes. These results provide insights into the structural organization within the hyaline layer as well as the role of the embryonic cell surface in maintaining the structural integrity of this extraembryonic matrix.