Cloning, sequencing and oocyte-specific expression of the marmoset sperm receptor protein, ZP3.

The zona pellucida surrounding the mammalian oocyte contains a major glycoprotein species, ZP3, that serves as a cell- and species-specific receptor for spermatozoa. In this study we have determined the primary amino acid structure of marmoset ZP3 (marZP3) and examined the expression of marZP3 mRNA within the ovary. The marZP3 gene possesses an open reading frame of 1272 nucleotides which is expressed specifically by the oocyte and encodes a polypeptide chain of 424 amino acids that exhibits 91% homology with the human ZP3 sequence. The disparity between these molecules was confined to a short domain spanning residues 322-352; otherwise the molecules were very similar, showing conservation of many structural features including the N-linked glycosylation sites, location and number of cysteine and proline residues and hydrophobicity profile. The results of this study have important implications for the use of the marmoset monkey as an animal model for the development of contraceptive vaccines targeting ZP3.