IDENTIFICATION AND STRUCTURAL CHARACTERIZATION OF THE 75-KDA RABBIT ZONA-PELLUCIDA PROTEIN

A cDNA (rc75) encoding a 75-kDa rabbit zona pellucida (ZP) glycoprotei n (R75) has been cloned and sequenced. The predicted amino acid sequen ce consists of 676 amino acids including seven potential N-glycosylati on sites. The cDNA hybridizes to a 2.4-kilobase mRNA in ovary that is not detectable in other rabbit tissues. The R75 mRNA was also found to be expressed during the early stages of rabbit ovarian development (2 -6 weeks of age) when the ovary contains primordial, primary, and earl y secondary follicles. The deduced amino acid sequence of rc75 has 77% similarity to the mouse ZP2 protein but no similarity to mouse ZP3. R 75 also contains regions with 35-55% similarity to a previously cloned rabbit 55-kDa ZP protein. Monte Carlo simulation comparison confirmed that R75 has a significant probability of homology with mouse ZP2 and the rabbit 55-kDa ZP protein. Antibodies were developed against a fra gment of R75 (rc75a cDNA) expressed in the pEX expression vector. Thes e antibodies were used to confirm that the expressed protein contained epitopes found in the native rabbit ZP glycoprotein. These data sugge st that some, but not all, ZP proteins may be conserved among differen t species and that within a species ZP proteins may share similar regi ons.