Dev Biol 2004 Aug 01;2721:191-202. doi: 10.1016/j.ydbio.2004.03.043.

Proteolytic cleavage of the cell surface protein p160 is required for detachment of the fertilization envelope in the sea urchin.

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Sea urchin eggs secrete a serine protease activity, CGSP1, at fertilization that is essential for the block to polyspermy. Several targets of this proteolytic activity on the plasma membrane were identified here using a cell surface biotinylation approach. Amino acid microsequencing of one of these proteins led to the identification of a 4.75-kb cDNA clone from a Strongylocentrotus purpuratus ovary cDNA library that encodes a 160-kDa protein called p160. This protein contains five CUB domains and a putative transmembrane domain suggesting that p160 is an integral membrane protein with protein-protein interaction motifs facing the extracellular matrix of the egg. Whole-mount immunolocalization studies demonstrate that p160 is on the surface of the egg, enriched at the tips of microvilli. The protein is removed at fertilization in a protease-dependent manner, and functional assays suggest that p160 serves to link the plasma membrane to the vitelline layer until fertilization. Thus, p160 is a key candidate for a vitelline-layer linker protein, the selective proteolysis of which functions in the block to polyspermy in the sea urchin egg.

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Genes referenced: cgsp1 LOC100887844 LOC115919910 LOC582189 LOC582875 LOC752081 LOC756768 mpp5 p160
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