Voltage-dependent activation of frog eggs by a sperm surface disintegrin peptide.
Fertilin, a sperm protein of the metalloprotease/disintegrin/cysteine-rich (MDC) family, plays a critical role in sperm-egg binding in mammals. Peptides corresponding to the disintegrin domain of fertilin and antibodies against fertilin have been shown to inhibit mammalian sperm-egg binding and fusion. A protein from the same family, xMDC16, was recently cloned from frog (Xenopus laevis) testis and was found to be involved in frog sperm-egg binding. Here we report that xMDC16 is localized predominantly on the posterior surface of egg jelly-activated sperm, and peptides from the disintegrin domain of this protein activate eggs when applied near the egg surface. Egg activation was dependent on (1) specific amino acid residues (KTX); (2) the presence of divalent cations, but not external Ca2+ alone; and (3) voltage across the egg plasma membrane. This is the first demonstration of egg activation in vertebrates by the surface application of a peptide derived from a sperm surface protein, supporting a model for egg activation that involves a signal transducing receptor for sperm in the egg's plasma membrane.
Section of Molecular and Cellular Biology, University of California at Davis, Davis, California, 95616, USA.
F M
FM
Shilling
C R
CR
Magie
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Nuccitelli
D000818:Animals; D002118:Calcium / Q000378:metabolism / Q000502:physiology; D002413:Cations, Divalent; D019483:Disintegrins / Q000032:analysis / Q000494:pharmacology*; D005260:Female; D008274:Magnesium / Q000502:physiology; D008297:Male; D008562:Membrane Glycoproteins / Q000032:analysis / Q000494:pharmacology*; D010063:Ovum / Q000502:physiology*; D018408:Patch-Clamp Techniques; D011993:Recombinant Fusion Proteins; D015398:Signal Transduction; D013084:Sperm-Ovum Interactions / Q000502:physiology*; D013094:Spermatozoa / Q000737:chemistry*; D014982:Xenopus laevis
D002413:Cations, Divalent; D019483:Disintegrins; D008562:Membrane Glycoproteins; D011993:Recombinant Fusion Proteins; D008274:Magnesium; D002118:Calcium