MOLECULAR CHARACTERIZATION OF A HAMSTER OVIDUCT-SPECIFIC GLYCOPROTEIN

There is growing evidence that the oviduct is not a passive conduit fo r gamete and embryo transport but serves a function for the gametes an d/or embryos. The oviductal epithelium secretes one or more specific g lycoproteins that associate with the egg after ovulation. Several publ ished reports including our preliminary studies have suggested that th e egg-associating glycoprotein(s) from the oviduct exists in several m ammalian species including golden hamster. However, little or almost n o biochemical characterization of the hamster oviduct-specific glycopr otein (HOGP) has been reported. To analyze the molecular structure of the HOGP in detail, we have attempted molecular cloning of cDNA corres ponding to HOGP. A cDNA library constructed from the hamster oviduct i n the phage vector lambda ZAPII was screened with digoxigenin-labeled, baboon oviduct-specific glycoprotein cDNA as the probe. A single posi tive clone was isolated, a nd the nucleotide sequence of the isolated cDNA was determined. Rapid amplification of cDNA end was carried out t o obtain a proximal 5' cDNA end of the clone. The cDNA clone consisted of 2387 bp, and the coding region contained 2013 bp translating to 67 1 amino acids. The amino acid sequence deduced from the cDNA sequence confirmed the chemically determined NH2-terminal sequence of a HOGP an d suggested that the derived amino acid sequence contained a signal pe ptide region (21 amino acids) and 650 amino acids (70 890 daltons) of the mature form of the HOGP region. The amino acid sequence of HOGP ap peared to have eight potential N-glycosylation sites, Northern blot an alysis revealed that a single message of approximately 2.5 kb was pres ent in oviductal RNA but not in the RNA of several other hamster tissu es, The HOOP showed high amino acid sequence homology with baboon, bov ine, and human oviduct-specific glycoprotein. These results demonstrat e that an oviduct-specific glycoprotein homologue gene exists in vario us mammalian species including rodent.