Echinonectin: a new embryonic substrate adhesion protein.

Abstract

Abstract. An extracellular matrix molecule has been purified from sea urchin (Lytechinus variegatus) embryos. Based on its functional properties and on its origin, this glycoprotein has been given the name "echinonectinY Echinonectin is a 230-kD dimer with a unique bow tie shape when viewed by electron microscopy. The molecule is 12 nm long, 8 nm wide at the ends, and narrows to ,o4 nm at the middle. It is composed of two ll6-kD U-shaped subunits that are attached to each other by disulfide bonds at their respective apices. Polyclonal antibodies were used to localize echinonectin in paraffin-embedded, sectioned specimens by indirect immunofluorescence. The protein is stored in vesicles or granules in unfertilized eggs, is released after fertilization, and later becomes localized on the apical surface of ectoderm cells in the embryo. When used as a substrate in a quantitative in vitro assay, echinonectin is highly effective as an adhesive substrate for dissociated embryonic cells. Because of the quantity, pattern of appearance, distribution, and adhesive characteristics of this protein, we suggest that echinonectin serves as a substrate adhesion molecule during sea urchin development.

Prasinoviruses of the Marine Green Alga Ostreococcus tauri Are Mainly Species Specific

“…Furthermore, glycosyltransferases encoded by viruses are considered important in the regulation of host-virus interactions, because they can fix glycans on proteins, lipids, or DNA, and consequently, they can modify the structure and function of proteins or make the viral DNA resistant to host restriction endonucleases (32). Among the proteins that might play a role in the viral adsorption, two are putative adhesin-like proteins: OtV5_074 is similar to a putative Hep-Hag family protein (23,67) and OtV5_120 is a putative echinonectin, an embryonic substrate adhesion protein found in sea urchin (3). Although OtV5_120 has no repeated motifs, Hep-Hag repeating residues found in bacterial hemagglutinins and invasins are known to exhibit binding activity (67).…”

Effects of Dithiothreitol on Protein Activity Unrelated to Thiol–Disulfide Exchange: For Consideration in the Analysis of Protein Function with Cleland's Reagent

“…Echinonectin, used as a positive control in Sepharose-binding assays, was isolated from unfertilized sea urchin eggs as previously described (4). The buffer system of Laemmli (5) was used for SDS-polyacrylamide gel electrophoresis.…”

Synthesis and secretion of molecules exhibiting the HL1 epitope during development of the hyaline layer of the asteroid pisaster ochraceus

“…When the HL of both sea urchins and starfish is dissolved using glycine/EDTA, the embryos/larvae dissociate into single cells. On the basis of these results, it has been proposed that elements of the HL provide a substrate for cell adhesion in sea urchins (Alliegro et al, 1988). Embryos/larvae of the sea urchin Pisaster ochraceus that have been exposed to sufficient HL1 antibody to cause sloughing remain intact, although their growth is stunted.…”

“…These include hyaline, proteoglycans, glycosaminoglycans, glycoproteins, laminin, and collagen (Spiegel and Spiegel, 1979;Adelson and Humphreys, 1988;Reimer and Crawford, 1990;Crawford and Crawford, 1992;Crawford et al, 1997). In echinoids studies on the secretion of the glycoprotein hyalin, as well as collagen, fibronectin, and laminin show that these molecules are not all released at fertilization but have distinct spatial and temporal expression patterns that extend for at least 30 h postfertilization (Alliegro et al, 1988;Matese et al, 1997). This suggests that, like the starfish HL, the sea urchin HL may also develop in a multistep fashion.…”