Protein composition of the hyaline layer of sea urchin embryos and reaggregating cells

The protein composition of the sea urchin embryo hyaline layer has been studied by 125I surface labeling. The electrophoretic patterns of iodinated proteins indicate that the composition of the hyaline layer is species and stage-specific. Dissociation of iodinated embryos removes some labeled proteins of apparent molecular weights of 290,000, 175,000, 145,000, 110,000, 70,000, and 50,000. The electrophoretic pattern of labeled proteins found in the intact embryo is reestablished on the surface of aggregates following reaggregation. The possible function of these proteins with respect to cell adhesion, cell-sorting behavior and morphogenesis is discussed.