Abstract. During fertilization, the sea urchin sperm acrosome reaction (AR), an ion channel-regulated event, is triggered by glycoproteins in egg jelly (E J). A 210-kD sperm membrane glycoprotein is the receptor for EJ (RE J). This conclusion is based on the following data: purified REJ binds species specifically to EJ dotted onto nitrocellulose, an mAb to REJ induces the sperm AR, antibody induction is blocked by purified RE J, and purified REJ absorbs the AR-inducing activity of EJ. Overlapping fragments of REJ cDNA were cloned (total length, 5,596 bp). The sequence was confirmed by microsequencing six peptides of mature REJ and by Western blotting with antibody to a synthetic peptide designed from the sequence. Complete deglycosylation of REJ followed by Western blotting yielded a size estimate in agreement with that of the mature amino acid sequence. REJ is modular in design; it contains one EGF module and two C-type lectin carbohydrate-recognition modules. Most importantly, it contains a novel module, herein named the REJ module (700 residues), which shares extensive homology with the human polycystic kidney disease protein (PKD1). Mutations in PKD1 cause autosomal dominant polycystic kidney disease, one of the most frequent genetic diseases of humans. The lesion in cellular physiology resuiting from mutations in the PKD1 protein remains unknown. The homology between REJ modules of the sea urchin REJ and human PKD1 suggests that PKD1 could be involved in ionic regulation. SEA urchin eggs possess an extracellular matrix termed egg jelly (E J) t. Glycoprotein ligands in EJ induce the sperm acrosome reaction (AR) (Keller and Vacquier, 1994a;Suzuki, 1995). The AR is required for fertilization; it consists of the exocytosis of the acrosome granule and the polymerization of acrosomal actin to form the bindin-coated acrosomal process used by the sperm to attach to and fuse with the egg (Vacquier et al., 1995). Underlying the E J-induced AR, increased sperm respiration,

SUMMARY Venom peptides from two species of fish-hunting cone snails (Conus striatus and Conus catus) were characterized using microbore liquid chromatography coupled with matrix-assisted laser desorption/ionization-time of flight-mass spectrometry and electrospray ionization-ion trap-mass spectrometry. Both crude venom isolated from the venom duct and injected venom obtained by milking were studied. Based on analysis of injected venom samples from individual snails, significant intraspecific variation (i.e. between individuals) in the peptide complement is observed. The mixture of peptides in injected venom is simpler than that in the crude duct venom from the same snail, and the composition of crude venom is more consistent from snail to snail. While there is animal-to-animal variation in the peptides present in the injected venom, the composition of any individual's injected venom remains relatively constant over time in captivity. Most of the Conus striatus individuals tested injected predominantly a combination of two neuroexcitatory peptides (s4a and s4b),while a few individuals had unique injected-venom profiles consisting of a combination of peptides, including several previously characterized from the venom duct of this species. Seven novel peptides were also putatively identified based on matches of their empirically derived masses to those predicted by published cDNA sequences. Profiling injected venom of Conus catus individuals using matrix-assisted laser desorption/ionization-time of flight-mass spectrometry demonstrates that intraspecific variation in the mixture of peptides extends to other species of piscivorous cone snails. The results of this study imply that novel regulatory mechanisms exist to select specific venom peptides for injection into prey.

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