STRUCTURE AND MACROMOLECULAR-COMPOSITION OF THE ZEBRAFISH EGG CHORION

The chorion is the acellular envelope surrounding mature eggs of teleo stean fish. The macromolecular composition of the zebrafish (Danio rer io) egg chorion, organised as a three-layered structure, has been anal ysed. SDS-PAGE analysis, under reducing conditions, of isolated and pu rified chorions revealed a reproducible pattern of four major polypept ides (116, 97, 50 and 43 kDa) and several minor bands. Lectin binding assays showed that both the 116 kDa and 50 kDa proteins were recognise d by concanavalin agglutinin (Con A), Galanthus nivalis agglutinin (GN A), Sambucus nigra bark agglutinin (SNA) and Ricinus communis agglutin in (RCA 120), suggesting that these polypeptides are N-linked glycopro teins. By contrast, neither the 97 kDa nor the 43 kDa polypeptides wer e stained by these lectins, indicating that these polypeptides are not glycosylated. Amino acid analysis also showed significant differences in the average content of some amino acids, for example serine and pr oline, when compared with previous reports.