Genomic organization and polypeptide primary structure of zona pellucida glycoprotein hZP3, the hamster sperm...

During the course of fertilization in mammals, free-swimming sperm bind tightly to receptors located in the egg extracellular coat, or zona pellucida. Recently, the hamster sperm receptor, a 56,000 Mr zona pellucida glycoprotein called hZP3, was identified and partially characterized (C. C. Moller et al., (1990). Dev. Biol. 137, 276-286). Here, we describe genomic cloning of hZP3, certain organizational features of the hZP3 gene, and primary structures of hZP3 mRNA and polypeptide. The findings are compared with reported results of comparable analyses of the mouse sperm receptor, an 83,000 Mr zona pellucida glycoprotein called mZP3. Such comparisons reveal a high degree of conservation of genomic organization and polypeptide structure for the two mammalian sperm receptors, despite the considerable difference in their Mrs. These findings are of interest in view of the extremely restricted expression of the ZP3 gene during development and the important role of ZP3 oligosaccharides in gamete adhesion.