Molecular cloning of a sperm fucosidase cDNA of Halocynthia roretzi

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Specific binding of spermatozoa to the vitelline coat is a necessary step for fertilization in various animals. In two ascidian species, Halocynthia roretzi and Ciona intestinalis, L-fucosyl residues of acidic saccharide chains in glycoproteins appear to beessential for the sperm-receptor activity of the vitelline coat. Sperm binding was blocked by specific inhibitors against fucosidase, and the fucosylamine affinity column adsorbed the sperm extract appreciably in normal sea water. It is thus suggested that sperm fucosidase play an important role in sperm binding to the vitelline coat.In the present study, we isolated the cDNA (HrFuc) encoding Halocynthia roretzi sperm alpha-L-fucosidase by RT-PCR method using the conservative region of alpha-L-fucosidase. The nucleotide and fucosidase were compared with the human, rat and Discoidium fucosidase sequences. The polyclonal antibody was prepared against a lacZ-HrFuc fusion protein made in Escherichia coli. Western analysis showed that this antibody crossed to 33 kDa sperm proteins. And this antibody inhibited ferterization in Halocynthia roretzi. Then, the cloned cDNA seems to be closedly corelated with the sperm-vitelline coat binding.