Abstract
A giant protein of apparent molecular weight ( M r) 2000 kDa, as determined by SDS-PAGE, was isolated and partially purified, under denaturing conditions, from the detergentresistant cytomatrix of unfertilized sea urchin egg. Immunoblot analysis and indirect immunofluorescence microscopy observations indicated that this highmolecularweight protein crossreacted with the immunospecific serum raised against chicken breast muscle β-connectin. However, rotaryshadowing electron microscopy images of the protein revealed short threadlike structures which appear morphologically different from β-connectin structure. Indirect immunofluorescence localization of the protein with antiβ-connectin serum showed a distribution throughout the whole unfertilized egg cytomatrix. This immunofluorescence pattern seems to change upon egg fertilization, since at metaphase the fluorescence stain appears to be excluded from the mitotic apparatus region as revealed by the double immunolabeling with anti-β-connectin serum and monoclonal anti-α-tubulin antibody. Moreover, when egg cortical fragments were doublelabeled with anti-β-connectin serum and rhodamin-conjugated phalloidin, it was observed that the microfilaments assembled after fertilization seem to be in close association with the protein at the cleavage furrow and other locations. The possible significance of this sea urchin egg connectin(titin)-like protein is discussed.
Published Version
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