The Journal of Cell Biology, Vol 116, 647-658, Copyright © 1992 by The Rockefeller University Press

ARTICLES

Identification of the sea urchin egg receptor for sperm using an antiserum raised against a fragment of its extracellular domain

KR Foltz and WJ Lennarz
Department of Biochemistry and Cell Biology, State University of New York, Stony Brook 11794-5215.

Sea urchin egg fertilization requires the species-specific interaction of molecules on the sperm and egg surfaces. Previously, we isolated an extracellular, 70-kD glycosylated fragment of the S. purpuratus egg receptor for sperm by treating the eggs with lysylendoproteinase C (Foltz, K. R., and W. J. Lennarz. 1990. J. Cell Biol. 111:2951-2959). To characterize the receptor further, we have generated a polyclonal antiserum (anti-70KL) against the purified 70-kD fragment. Anti-70KL was found to react with a single polypeptide of approximately 350 kD on Western blots, presumed to be the intact receptor, in an egg cell surface preparation. This polypeptide appeared to be tightly associated with the plasma membrane/vitelline layer complex, as it was released from these preparations only by detergent treatment. Immunofluorescence microscopy revealed that the receptor was distributed evenly over the egg surface. The anti-70KL was species specific both in its ability to recognize the egg surface protein and to inhibit sperm binding. Fab fragments generated from affinity-purified anti-70KL also bound to the egg surface and inhibited sperm binding in a concentration-dependent manner. Interestingly, treatment with Fabs caused a small percentage of eggs to undergo cortical granule exocytosis, even in the absence of external Ca2+. These results confirm earlier findings indicating that the receptor is a cell surface glycoprotein of high molecular weight that species specifically binds sperm. This antiserum provides a powerful tool for further investigation of gamete interactions and the structure of the sperm receptor.
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This article has been cited by other articles:

• Wilson, N. F., Foglesong, M. J., Snell, W. J. (1997). The Chlamydomonas Mating Type Plus Fertilization Tubule, a Prototypic Cell Fusion Organelle: Isolation, Characterization, and In Vitro Adhesion to Mating Type Minus Gametes. JCB 137: 1537-1553 [Abstract] [Full Text]  
• Foltz, K., Partin, J., Lennarz, W. (1993). Sea urchin egg receptor for sperm: sequence similarity of binding domain and hsp70. Science 259: 1421-1425 [Abstract]  

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