MOLECULAR-CLONING AND CHARACTERIZATION OF AN ESTROGEN-DEPENDENT PORCINE OVIDUCTAL SECRETORY GLYCOPROTEIN

A family of estrogen-dependent porcine oviductal secretory glycoprotei ns (POSPs) that exhibit structural similarities are synthesized and se creted into the oviductal lumen at proestrus, estrus, and metestrus. T he objectives of this study were to clone the POSP cDNA, obtain the fu ll-length cDNA and protein sequence, examine tissue specificity and sp ecies distribution, characterize its regulation, and establish its ide ntity by comparison to other known protein, RNA, or DNA sequences. A f ull-length cDNA of 2022 base pairs was obtained with an open reading f rame of 1581 nucleotides, coding for a deduced protein of 527 amino ac ids (57 970 M(r)). The deduced protein contained three potential N-gly cosylation sites, a consensus heparin-binding site, and potential O-gl ycosylation sites. Amino acid analysis of POSP-E3 confirmed the presen ce of a 21-amino acid signal sequence. Northern blot analysis revealed an oviduct-specific mRNA species of 2.25 kb in the infundibulum (INF) , ampulla (A), and isthmus (1). An mRNA of similar size was detected i n the oviduct of the sheep, cow, and rabbit, and one of slightly great er size (2.8 kb) in the mouse and hamster oviduct but not in the horse or alligator oviduct. Dot blot analysis indicated that steady-state l evels of POSP mRNA were significantly greater (p = 0.0001) in the A th an in the INF or I regardless of day of the estrous cycle and were gre ater on Day 0 (estrus; p = 0.0001) regardless of location. Further, st eady-state mRNA levels were significantly increased (p = 0.02) on Days 0 and 1, declining rapidly to Day 2 through Day 15 of the estrous cyc le. Steady-state POSP mRNA levels were significantly greater (p < 0.00 3) in ovariectomized gilts treated with estradiol valerate than those treated with other steroid regimens, vehicle, or no treatment (Control ), consistent with estrogen control of mRNA expression. The POSP prote in exhibited significant identity to oviductal glycoproteins from the baboon, cow, hamster, human, mouse, and sheep; to several mammalian no noviductal glycoproteins; and to several chitinases. POSP joins a grow ing subfamily of the chitinase gene family that lacks chitinase enzyma tic activity.